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Chapter 5. Test cases

After finishing the installation, it is recommended to run some basic tests to check the installation and verify how SAP HANA Multitarget System Replication is working and how it recovers from a failure. It is always a good practice to run these test cases before starting production. If possible, you can also prepare a test environment to verify changes before starting production. If possible, you can also prepare a test environment to check the changes before applying them in production.

All cases will describe:

  • Subject of the test
  • Test preconditions
  • Test steps
  • Monitoring the test
  • Starting the test
  • Expected result(s)
  • Ways to return to an initial state

To automatically register a former primary HANA replication site as a new secondary HANA replication site on the HANA instances that are managed by the cluster, you can use the option AUTOMATED_REGISTER=true in the SAPHana resource. For more details, refer to AUTOMATED_REGISTER.

The name of the HA cluster nodes and the HANA replication sites (in brackets) used in the examples are:

  • clusternode1 (DC1)
  • clusternode2 (DC2)
  • remotehost3 (DC3)

The following parameters are used for configuring the HANA instances and the cluster:

  • SID=RH2
  • INSTANCENUMBER=02
  • CLUSTERNAME=cluster1

You can use clusternode1-2, remotehost3 also as alias in the /etc/hosts in your test environment.

The tests are described in more detail, including examples and additional checks of preconditions. At the end, there are examples of how to clean up the environment to be prepared for further testing.

In some cases, if the distance between clusternode1-2 and remotehost3 is too long, you should use –replcationMode=async instead of –replicationMode=syncmem. Please also ask your SAP HANA administrator before choosing the right option.

5.1. Prepare the tests
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Before we run a test, the complete environment needs to be in a correct and healthy state.

We have to check the cluster and the database via:

  • pcs status --full
  • python $DIR_EXECUTABLE/python_support/systemReplicationStatus.py
  • df -h

An example for pcs status --full can be found in Check cluster status with pcs status. If there are warnings or previous failures in the "Migration Summary", you should clean up the cluster before you start your test.

[root@clusternode1]# pcs resource clear SAPHana_RH2_02-clone
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Cluster Cleanup describes some more ways to do it. It is important that the cluster and all the resources be started.

Besides the cluster, the database should also be up and running and in sync. The easiest way to verify the proper status of the database is to check the system replication status. See also Replication Status. This should be checked on the primary database.

To discover the primary node, you can check Discover Primary Database or use: 

[root@clusternode1]# pcs status | grep -E "Promoted|Master"
[root@clusternode1]# hdbnsutil -sr_stateConfiguration
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Check if there is enough space on the file systems by running: 

[root@clusternode1]# df -h
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Please also follow the guidelines for a system check before you continue. If the environment is clean, it is ready to run the tests.

5.2. Monitor the environment
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In this section, we are focusing on monitoring the environment during the tests. This section will only cover the necessary monitors to see the changes. It is recommended to run these monitors from dedicated terminals. To be able to detect changes during the test, it is recommended to start monitoring before starting the test.

In the Useful Commands section, more examples are shown.

5.2.1. Discover the primary node
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You need to discover the primary node to monitor a failover or run certain commands that only provide information about the replication status when executed on the primary node.

To discover the primary node, you can run the following commands as the <sid>adm user: 

clusternode1:rh2adm> watch -n 5 'hdbnsutil -sr_stateConfiguration | egrep -e "primary masters|^mode"'
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Output example, when clusternode2 is the primary database: 

mode: syncmem
primary masters: clusternode2
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Output on the node that runs the primary database is: 

mode: primary
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5.2.2. Check the Replication status
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The replication status shows the relationship between primary and secondary database nodes and the current status of the replication.

To discover the replication status, you can run as the <sid>adm user: 

clusternode1:rh2adm> hdbnsutil -sr_stateConfiguration
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If you want to permanently monitor changes in the system replication status, please run the following command: 

clusternode1:rh2adm> watch -n 5 'python /usr/sap/${SAPSYSTEMNAME}/HDB${TINSTANCE}/exe/python_support/systemReplicationStatus.py ; echo Status $?'
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This example also determines the current return code.
As long as the return code (status) is 15, the replication status is fine. The other return codes are:

  • 10: NoHSR
  • 11: Error
  • 12: Unknown
  • 13: Initializing
  • 14: Syncing
  • 15: Active

If you register a new secondary, you can run it in a separate window on the primary node and you will see the progress of the replication. If you want to monitor a failover, you can run it in parallel on the old primary as well as on the new primary database server. For more information, please read Check SAP HANA System Replication Status.

5.2.3. Check /var/log/messages entries
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Pacemaker is writing a lot of information into the /var/log/messages file. During a failover, a huge number of messages are written into this message file. To be able to follow only the important messages depending on the SAP HANA resource agent, it is useful to filter the detailed activities of the pacemaker SAP resources. It is enough to check the messages file on a single cluster node.

For example, you can use this alias: 

[root@clusternode1]# alias tmsl='tail -1000f /var/log/messages | egrep -s "Setting master-rsc_SAPHana_$SAPSYSTEMNAME_HDB${TINSTANCE}|sr_register|WAITING4LPA|PROMOTED|DEMOTED|UNDEFINED|master_walk|SWAIT|WaitforStopped|FAILED|LPT"'
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Run tmsl in a separate window to monitor the progress of the test. Please also check the example Monitor failover and sync state.

5.2.4. Cluster status
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There are several ways to check the cluster status.

  • Check if the cluster is running:

    • pcs cluster status

  • Check the cluster and all resources:

    • pcs status

  • Check the cluster, all resources and all node attributes:

    • pcs status --full

  • Check the resources only:

    • pcs resource

The pcs status --full command will give you all the necessary information. To monitor changes, you can run this command together with watch: 

[root@clusternode1]# watch pcs status --full
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An output example and further options can be found in Check cluster status.

5.2.5. Discover leftovers
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To ensure that your environment is ready to run the next test, leftovers from previous tests need to be fixed or removed.

  • stonith is used to fence a node in the cluster:

    • Detect: [root@clusternode1]# pcs stonith history
    • Fix: [root@clusternode1]# pcs stonith cleanup

  • Multiple primary databases:

    • Detect: clusternode1:rh2adm> hdbnsutil -sr_stateConfiguration | grep -i primary

      All nodes with the same primary need to be identified.

    • Fix: re-register the wrong primary with option --force_full_replica

  • Location Constraints caused by move:

    • Detect: [root@clusternode1]# pcs constraint location

      Check the warning section.

    • Fix: [root@clusternode1]# pcs resource clear <clone-resource-which was moved>

  • Secondary replication relationship:

    • Detect: on the primary database run clusternode1:rh2adm> python $DIR_EXECUTABLE/python_support/systemReplicationStatus.py
    • Fix: unregister and re-register the secondary databases.

  • Check siteReplicationMode (same output on all SAP HANA nodes)

    • clusternode1:rh2adm> hdbnsutil -sr_state --sapcontrol=1 |grep site.*Mode

  • Pcs property:

    • Detect: [root@clusternode1]# pcs property config
    • Fix: [root@clusternode1]# pcs property set <key=value>

  • Clear maintenance-mode.

    • [root@clusternode1]# pcs property set maintenance-mode=false

  • log_mode:

    • Detect: clusternode1:rh2adm> python systemReplicationStatus.py

      Will respond in the replication status that log_mode normally is required. log_mode can be detected as described in Using hdbsql to check Inifile contents.

    • Fix: change the log_mode to normal and restart the primary database.

  • CIB entries:

    • Detect: SFAIL entries in the cluster information base.

      Please refer to Check cluster consistency, to find and remove CIB entries.

  • Cleanup/clear:

    • Detect: [root@clusternode1]# pcs status --full

      Sometimes it shows errors or warnings. You can cleanup/clear resources and if everything is fine, nothing happens. Before running the next test, you can cleanup your environment.

    • Examples to fix:

      [root@clusternode1]# pcs resource clear <name-of-the-clone-resource>[root@clusternode1]# pcs resource cleanup <name-of-the-clone-resource>

This is also useful if you want to check if there is an issue in an existing environment.

For more information, please refer to Useful commands.

Expand

Subject of the test

Automatic re-registration of the third site.

Sync state changes to SOK after clearing.

Test preconditions

  • SAP HANA on DC1, DC2, DC3 are running.
  • Cluster is up and running without errors or warnings.

Test steps

Move the SAPHana resource using the pcs [root@clusternode1]# resource move <sap-clone-resource> <target-node> command.

Monitoring the test

On the third site run as rh2adm the command provided at the end of table.(*)

On the secondary node run as root: [root@clusternode1]# watch pcs status --full

Starting the test

Execute the cluster command:

[root@clusternode1]# pcs move resource SAPHana_RH2_02-clone <target-node>

[root@clusternode1]# pcs resource clear SAPHana_RH2_02-clone

Expected result

In the monitor command on site 3 the primary master changes from clusternode1 to clusternode2.

After clearing the resource the sync state will change from SFAIL to SOK.

Ways to return to an initial state

Run the test twice.

(*) 

remotehost3:rh2adm>
watch hdbnsutil -sr_state
[root@clusternode1]# tail -1000f /var/log/messages |egrep -e ‘SOK|SWAIT|SFAIL’
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Detailed description

  • Check the initial state of your cluster as root on clusternode1 or clusternode2. 

    [root@clusternode1]# pcs status --full
Cluster name: cluster1
Cluster Summary:
  * Stack: corosync
  * Current DC: clusternode1 (1) (version 2.1.2-4.el8_6.6-ada5c3b36e2) - partition with quorum
  * Last updated: Mon Sep  4 06:34:46 2023
  * Last change:  Mon Sep  4 06:33:04 2023 by root via crm_attribute on clusternode1
  * 2 nodes configured
  * 6 resource instances configured

Node List:
  * Online: [ clusternode1 (1) clusternode2 (2) ]

Full List of Resources:
  * auto_rhevm_fence1	(stonith:fence_rhevm):	 Started clusternode1
  * Clone Set: SAPHanaTopology_RH2_02-clone [SAPHanaTopology_RH2_02]:
    * SAPHanaTopology_RH2_02	(ocf::heartbeat:SAPHanaTopology):	 Started clusternode2
    * SAPHanaTopology_RH2_02	(ocf::heartbeat:SAPHanaTopology):	 Started clusternode1
  * Clone Set: SAPHana_RH2_02-clone [SAPHana_RH2_02] (promotable):
    * SAPHana_RH2_02	(ocf::heartbeat:SAPHana):	 Slave clusternode2
    * SAPHana_RH2_02	(ocf::heartbeat:SAPHana):	 Master clusternode1
  * vip_RH2_02_MASTER	(ocf::heartbeat:IPaddr2):	 Started clusternode1

Node Attributes:
  * Node: clusternode1 (1):
    * hana_rh2_clone_state            	: PROMOTED
    * hana_rh2_op_mode                	: logreplay
    * hana_rh2_remoteHost             	: clusternode2
    * hana_rh2_roles                  	: 4:P:master1:master:worker:master
    * hana_rh2_site                   	: DC1
    * hana_rh2_sra                    	: -
    * hana_rh2_srah                   	: -
    * hana_rh2_srmode                 	: syncmem
    * hana_rh2_sync_state             	: PRIM
    * hana_rh2_version                	: 2.00.062.00
    * hana_rh2_vhost                  	: clusternode1
    * lpa_rh2_lpt                     	: 1693809184
    * master-SAPHana_RH2_02           	: 150
  * Node: clusternode2 (2):
    * hana_rh2_clone_state            	: DEMOTED
    * hana_rh2_op_mode                	: logreplay
    * hana_rh2_remoteHost             	: clusternode1
    * hana_rh2_roles                  	: 4:S:master1:master:worker:master
    * hana_rh2_site                   	: DC2
    * hana_rh2_sra                    	: -
    * hana_rh2_srah                   	: -
    * hana_rh2_srmode                 	: syncmem
    * hana_rh2_sync_state             	: SOK
    * hana_rh2_version                	: 2.00.062.00
    * hana_rh2_vhost                  	: clusternode2
    * lpa_rh2_lpt                     	: 30
    * master-SAPHana_RH2_02           	: 100

Migration Summary:

Tickets:

PCSD Status:
  clusternode1: Online
  clusternode2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled
    Copy to Clipboard Toggle word wrap

    This output shows you that HANA is promoted on clusternode1, which is the primary SAP HANA server and that the name of the clone resource is SAPHana_RH2_02-clone which is promotable.
    You can run this in a separate window during the test to see changes: 

    [root@clusternode1]# watch pcs status --full
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  • Another way to identify the name of the SAP HANA clone resource is: 

    [root@clusternode2]# pcs resource
  * Clone Set: SAPHanaTopology_RH2_02-clone [SAPHanaTopology_RH2_02]:
    * Started: [ clusternode1 clusternode2 ]
  * Clone Set: SAPHana_RH2_02-clone [SAPHana_RH2_02] (promotable):
    * Promoted: [ clusternode2 ]
    * Unpromoted: [ clusternode1 ]
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  • To see the change of the primary server start monitoring on remotehost3 on a separate terminal window before you start the test. 

    remotehost3:rh2adm> watch 'hdbnsutil -sr_state | grep "primary masters"
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    The output will look like: 

    Every 2.0s: hdbnsutil -sr_state | grep "primary masters"                                                                                 remotehost3: Mon Sep  4 08:47:21 2023

primary masters: clusternode1
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    During the test the expected output will change to clusternode2.

  • Start the test by moving the clone resource discovered above to clusternode2: 

    [root@clusternode1]# pcs resource move SAPhana_RH2_02-clone clusternode2
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  • The output of the monitor on remotehost3 will change to: 

    Every 2.0s: hdbnsutil -sr_state | grep "primary masters"
remotehost3: Mon Sep  4 08:50:31 2023

primary masters: clusternode2
    Copy to Clipboard Toggle word wrap

    Pacemaker creates a location constraint for moving the clone resource. This needs to be manually removed. You can see the constraint using: 

    [root@clusternode1]# pcs constraint location
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    This constraint needs to be removed.

  • Clear the clone resource to remove the location constraint: 

    [root@clusternode1]#  pcs resource clear SAPhana_RH2_02-clone
Removing constraint: cli-prefer-SAPHana_RH2_02-clone
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  • Cleanup the resource: 

    [root@clusternode1]# pcs resource cleanup SAPHana_RH2_02-clone
Cleaned up SAPHana_RH2_02:0 on clusternode2
Cleaned up SAPHana_RH2_02:1 on clusternode1
Waiting for 1 reply from the controller
... got reply (done)
    Copy to Clipboard Toggle word wrap

Result of the test

  • The “primary masters” monitor on remotehost3 should show an immediate switch to the new primary node.
  • If you check the cluster status, the former secondary will be promoted, the former primary gets re-register and the Clone_State changes from Promoted to Undefined to WAITINGFORLPA to DEMOTED.
  • The secondary will change the sync_state to SFAIL when the SAPHana monitor is started for the first time after the failover. Because of existing location constraints the resource needs to be cleared and after a short time the sync_state of the secondary will change to SOK again.
  • Secondary gets promoted.

To restore the initial state you can simply run the next test. After finishing the tests please run a cleanup.

Expand

Subject of the test

No re-registration of the stopped third site.

Failover works even if the third site is down.

Test preconditions

  • SAP HANA on DC1, DC2 is running and is stopped on DC3.
  • Cluster is up and running without errors or warnings.

Test steps

Move the SAPHana resource using the pcs [root@clusternode1]# resource move command.

Starting the test

Execute the cluster command: [root@clusterclusternode1]# pcs move resource SAPHana_RH2_02-clone clusterclusternode1

Expected result

No change on DC3. SAP HANA System Replication stays on old relationship.

Ways to return to an initial state

Re-register DC3 on new primary and start SAP HANA.

Detailed description

  • Check the initial state of your cluster as root on clusternode1 or clusternode2: 

    [root@clusternode1]# pcs status --full
Cluster name: cluster1
Cluster Summary:
  * Stack: corosync
  * Current DC: clusternode1 (1) (version 2.1.2-4.el8_6.6-ada5c3b36e2) - partition with quorum
  * Last updated: Mon Sep  4 06:34:46 2023
  * Last change:  Mon Sep  4 06:33:04 2023 by root via crm_attribute on clusternode1
  * 2 nodes configured
  * 6 resource instances configured

Node List:
  * Online: [ clusternode1 (1) clusternode2 (2) ]

Full List of Resources:
  * auto_rhevm_fence1	(stonith:fence_rhevm):	 Started clusternode1
  * Clone Set: SAPHanaTopology_RH2_02-clone [SAPHanaTopology_RH2_02]:
    * SAPHanaTopology_RH2_02	(ocf::heartbeat:SAPHanaTopology):	 Started clusternode2
    * SAPHanaTopology_RH2_02	(ocf::heartbeat:SAPHanaTopology):	 Started clusternode1
  * Clone Set: SAPHana_RH2_02-clone [SAPHana_RH2_02] (promotable):
    * SAPHana_RH2_02	(ocf::heartbeat:SAPHana):	 Slave clusternode2
    * SAPHana_RH2_02	(ocf::heartbeat:SAPHana):	 Master clusternode1
  * vip_RH2_02_MASTER	(ocf::heartbeat:IPaddr2):	 Started clusternode1

Node Attributes:
  * Node: clusternode1 (1):
    * hana_rh2_clone_state            	: PROMOTED
    * hana_rh2_op_mode                	: logreplay
    * hana_rh2_remoteHost             	: clusternode2
    * hana_rh2_roles                  	: 4:P:master1:master:worker:master
    * hana_rh2_site                   	: DC1
    * hana_rh2_sra                    	: -
    * hana_rh2_srah                   	: -
    * hana_rh2_srmode                 	: syncmem
    * hana_rh2_sync_state             	: PRIM
    * hana_rh2_version                	: 2.00.062.00
    * hana_rh2_vhost                  	: clusternode1
    * lpa_rh2_lpt                     	: 1693809184
    * master-SAPHana_RH2_02           	: 150
  * Node: clusternode2 (2):
    * hana_rh2_clone_state            	: DEMOTED
    * hana_rh2_op_mode                	: logreplay
    * hana_rh2_remoteHost             	: clusternode1
    * hana_rh2_roles                  	: 4:S:master1:master:worker:master
     * hana_rh2_site                   	: DC2
    * hana_rh2_sra                    	: -
    * hana_rh2_srah                   	: -
    * hana_rh2_srmode                 	: syncmem
    * hana_rh2_sync_state             	: SOK
    * hana_rh2_version                	: 2.00.062.00
    * hana_rh2_vhost                  	: clusternode2
    * lpa_rh2_lpt                     	: 30
    * master-SAPHana_RH2_02           	: 100

Migration Summary:

Tickets:

PCSD Status:
  clusternode1: Online
  clusternode2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled
    Copy to Clipboard Toggle word wrap

    The output of this example shows you that HANA is promoted on clusternode1, which is the primary SAP HANA server, and that the name of the clone resource is SAPHana_RH2_02-clone, which is promotable. If you run test 3 before HANA, you might be promoted on clusternode2.

  • Stop the database on remotehost3: 

    remotehost3:rh2adm> HDB stop
hdbdaemon will wait maximal 300 seconds for NewDB services finishing.
Stopping instance using: /usr/sap/RH2/SYS/exe/hdb/sapcontrol -prot NI_HTTP -nr 02 -function Stop 400

12.07.2023 11:33:14
Stop
OK
Waiting for stopped instance using: /usr/sap/RH2/SYS/exe/hdb/sapcontrol -prot NI_HTTP -nr 02 -function WaitforStopped 600 2


12.07.2023 11:33:30
WaitforStopped
OK
hdbdaemon is stopped.
    Copy to Clipboard Toggle word wrap

  • Check the primary database on remotehost3: 

    remotehost3:rh2adm> hdbnsutil -sr_stateConfiguration| grep -i "primary masters"

primary masters: clusterclusternode2
    Copy to Clipboard Toggle word wrap

  • Check the current primary in the cluster on a cluster node: 

    [root@clusterclusternode1]# pcs resource | grep Masters
    * Masters: [ clusternode2 ]
    Copy to Clipboard Toggle word wrap

  • Check the sr_state to see the SAP HANA System Replication relationships: 

    clusternode2:rh2adm> hdbnsutil -sr_state

System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~

online: true

mode: primary
operation mode: primary
site id: 2
site name: DC1

is source system: true
is secondary/consumer system: false
has secondaries/consumers attached: true
is a takeover active: false
is primary suspended: false

Host Mappings:
~~~~~~~~~~~~~~

clusternode1 -> [DC3] remotehost3
clusternode1 -> [DC1] clusternode1
clusternode1 -> [DC2] clusternode2


Site Mappings:
~~~~~~~~~~~~~~
DC1 (primary/primary)
    |---DC3 (syncmem/logreplay)
    |---DC2 (syncmem/logreplay)

Tier of DC1: 1
Tier of DC3: 2
Tier of DC2: 2

Replication mode of DC1: primary
Replication mode of DC3: syncmem
Replication mode of DC2: syncmem

Operation mode of DC1: primary
Operation mode of DC3: logreplay
Operation mode of DC2: logreplay

Mapping: DC1 -> DC3
Mapping: DC1 -> DC2
done.
    Copy to Clipboard Toggle word wrap

The SAP HANA System Replication relations still have one primary (DC1), which is replicated to DC2 and DC3. The replication relationship on remotehost3, which is down, can be displayed using: 

remothost3:rh2adm> hdbnsutil -sr_stateConfiguration

System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~

mode: syncmem
site id: 3
site name: DC3
active primary site: 1

primary masters: clusternode1
done.
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The database on remotehost3 which is offline checks the entries in the global.ini file.

  • Starting the test: Initiate a failover in the cluster, moving the SAPHana-clone-resource example: 

    [root@clusternode1]# pcs resource move SAPHana_RH2_02-clone clusternode2
    Copy to Clipboard Toggle word wrap
    Note

    If SAPHana is promoted on clusternode2, you have to move the clone resource to clusternode1. The example expects that SAPHana is promoted on clusternode1.

    There will be no output. Similar to the former test a location constraint will be created, which can be display with: 

    [root@clusternode1]# pcs constraint location
Location Constraints:
  Resource: SAPHana_RH2_02-clone
    Enabled on:
      Node: clusternode1 (score:INFINITY) (role:Started)
    Copy to Clipboard Toggle word wrap

    Even if the cluster looks fine again, this constraint avoids another failover unless the constraint is removed. One way is to clear the resource.

  • Clear the resource: 

    [root@clusternode1]# pcs constraint location
Location Constraints:
  Resource: SAPHana_RH2_02-clone
    Enabled on:
      Node: clusternode1 (score:INFINITY) (role:Started)
[root@clusternode1]# pcs resource clear SAPHana_RH2_02-clone
Removing constraint: cli-prefer-SAPHana_RH2_02-clone
    Copy to Clipboard Toggle word wrap

  • Cleanup the resource: 

    [root@clusternode1]# pcs resource cleanup SAPHana_RH2_02-clone
Cleaned up SAPHana_RH2_02:0 on clusternode2
Cleaned up SAPHana_RH2_02:1 on clusternode1
Waiting for 1 reply from the controller
... got reply (done)
    Copy to Clipboard Toggle word wrap

  • Check the current status. There are three ways to display the replication status which needs to be in sync. Starting with the primary on remotehost3: 

    remotehost3:rh2adm>  hdbnsutil -sr_stateConfiguration| grep -i primary
active primary site: 1
primary masters: clusternode1
    Copy to Clipboard Toggle word wrap

    The output shows site 1 or clusternode1 which was the primary before starting the test to move the primary to clusternode2. Next check the system replication status on the new primary. First detect the new primary: 

    [root@clusternode1]# pcs resource | grep  Master
    * Masters: [ clusternode2 ]
    Copy to Clipboard Toggle word wrap

    Here we have an inconsistency which requires to re-register remotehost3. You might think, if we run the test again, we might switch the primary back to the original clusternode1. In this case, we have a third way to identify if system replication is working. On the primary node, which is our case clusternode2 run: 

    clusternode2:rh2adm> cdpy
clusternode2:rh2adm> python
$DIR_EXECUTABLE/python_support/systemReplicationStatus.py
|Database |Host   |Port  |Service Name |Volume ID |Site ID |Site Name |Secondary |Secondary |Secondary |Secondary |Secondary     |Replication |Replication |Replication    |Secondary    |
|         |       |      |             |          |        |          |Host      |Port      |Site ID   |Site Name |Active Status |Mode        |Status      |Status Details |Fully Synced |
|-------- |------ |----- |------------ |--------- |------- |--------- |--------- |--------- |--------- |--------- |------------- |----------- |----------- |-------------- |------------ |
|SYSTEMDB |clusternode2 |30201 |nameserver   |        1 |      2 |DC2       |clusternode1    |    30201 |        1 |DC1       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |clusternode2 |30207 |xsengine     |        2 |      2 |DC2       |clusternode1    |    30207 |        1 |DC1       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |clusternode2 |30203 |indexserver  |        3 |      2 |DC2       |clusternode1    |    30203 |        1 |DC1       |YES           |SYNCMEM     |ACTIVE      |               |        True |

status system replication site "1": ACTIVE
overall system replication status: ACTIVE

Local System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

mode: PRIMARY
site id: 2
site name: DC2
    Copy to Clipboard Toggle word wrap

    If you don’t see remotehost3 in this output, you have to re-register remotehost3. Before registering, please run the following on the primary node to watch the progress of the registration: 

    clusternode2:rh2adm> watch python
$DIR_EXECUTABLE/python_support/systemReplicationStatus.py
    Copy to Clipboard Toggle word wrap

    Now you can re-register remotehost3 using this command: 

    remotehost3:rh2adm> hdbnsutil -sr_register --remoteHost=clusternode2 --remoteInstance=${TINSTANCE} --replicationMode=async --name=DC3 --remoteName=DC2 --operation
Mode=logreplay --online
adding site ...
collecting information ...
updating local ini files ...
done.
    Copy to Clipboard Toggle word wrap

    Even if the database on remotehost3 is not started yet, you are able to see the third site in the system replication status output.
    The registration can be finished by starting the database on remotehost3: 

    remotehost3:rh2adm> HDB start


StartService
Impromptu CCC initialization by 'rscpCInit'.
  See SAP note 1266393.
OK
OK
Starting instance using: /usr/sap/RH2/SYS/exe/hdb/sapcontrol -prot NI_HTTP -nr 02 -function StartWait 2700 2


04.09.2023 11:36:47
Start
OK
    Copy to Clipboard Toggle word wrap

The monitor started above will immediately show the synchronization of remotehost3.

  • To switch back, run the test again. One optional test is to switch the primary to the node, which is configured on the global.ini on remotehost3 and then starting the database. The database might come up, but it will never be shown in the output of the system replication status, unless it is re-registered.

For more information please also check Check SAP HANA System Replication status.

Expand

Subject of the test

Failover the primary to the third site.

Secondary will be re-registered to third site.

Test preconditions

  • SAP HANA on DC1, DC2, DC3 is running.
  • Cluster is up and running without errors or warnings.
  • System Replication is in place and in sync (check python systemReplicationStatus.py).

Test steps

Put the cluster into maintenance-mode to be able to recover.

Takeover the HANA database form the third node using: hdbnsutil -sr_takeover

Starting the test

Execute the SAP HANA commandon remotehost3: rh2adm>: hdbnsutil -sr_takeover

Monitoring the test

On the third site run: remotehost3:rh2adm> watch hdbnsutil -sr_state

Expected result

  • Third node will become primary.
  • Secondary node will change the primary master to remotehost3. Former primary node needs to be re-registered to the new primary.

Ways to return to an initial state

Run Test 4: Failback of the primary node to the first site.

Detailed description

  • Check if the databases are running using Check database and check the replication status: 

    clusternode2:rh2adm> hdbnsutil -sr_state | egrep -e "^mode:|primary masters"
    Copy to Clipboard Toggle word wrap

The output is for example: 

mode: syncmem
primary masters: clusternode1
Copy to Clipboard Toggle word wrap

In this case the primary database is clusternode1. If you run this command on clusternode1 you will get: 

mode: primary
Copy to Clipboard Toggle word wrap

On this primary node you can also display the system replication status. It should look like: 

clusternode1:rh2adm> cdpy
clusternode1:rh2adm> python systemReplicationStatus.py
|Database |Host   |Port  |Service Name |Volume ID |Site ID |Site Name |Secondary |Secondary |Secondary |Secondary |Secondary     |Replication |Replication |Replication    |Secondary    |
|         |       |      |             |          |        |          |Host      |Port      |Site ID   |Site Name |Active Status |Mode        |Status      |Status Details |Fully Synced |
|-------- |------ |----- |------------ |--------- |------- |--------- |--------- |--------- |--------- |--------- |------------- |----------- |----------- |-------------- |------------ |
|SYSTEMDB |clusternode1 |30201 |nameserver   |        1 |      1 |DC1       |remotehost3    |    30201 |        3 |DC3       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |clusternode1 |30207 |xsengine     |        2 |      1 |DC1       |remotehost3    |    30207 |        3 |DC3       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |clusternode1 |30203 |indexserver  |        3 |      1 |DC1       |remotehost3    |    30203 |        3 |DC3       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|SYSTEMDB |clusternode1 |30201 |nameserver   |        1 |      1 |DC1       |clusternode2    |    30201 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |clusternode1 |30207 |xsengine     |        2 |      1 |DC1       |clusternode2    |    30207 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |clusternode1 |30203 |indexserver  |        3 |      1 |DC1       |clusternode2    |    30203 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |

status system replication site "3": ACTIVE
status system replication site "2": ACTIVE
overall system replication status: ACTIVE

Local System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

mode: PRIMARY
site id: 1
site name: DC1
Copy to Clipboard Toggle word wrap
  • Now we have a proper environment and we can start monitoring the system replication status on all 3 nodes in separate windows.

The 3 monitors should be started before the test is started. The output will change when the test is executed. So keep them running as long as the test is not completed.

On the old primary node, clusternode1 ran in a separate window during the test: 

clusternode1:rh2adm> watch -n 5 'python /usr/sap/$SAPSYSTEMNAME/HDB${TINSTANCE}/exe/python_support/systemReplicationStatus.py ; echo Status $?`
Copy to Clipboard Toggle word wrap

The output on clusternode1 will be: 

Every 5.0s: python /usr/sap/$SAPSYSTEMNAME/HDB${TINSTANCE}/exe/python_support/systemReplicati...  clusternode1: Tue XXX XX HH:MM:SS 2023

|Database |Host   |Port  |Service Name |Volume ID |Site ID |Site Name |Secondary |Secondary |Secondary |Secondary |Secondary     |
Replication |Replication |Replication    |Secondary    |
|         |	  |	 |             |          |        |          |Host	 |Port      |Site ID   |Site Name |Active Status |
Mode        |Status	 |Status Details |Fully Synced |
|-------- |------ |----- |------------ |--------- |------- |--------- |--------- |--------- |--------- |--------- |------------- |
----------- |----------- |-------------- |------------ |
|SYSTEMDB |clusternode1 |30201 |nameserver   |        1 |	 1 |DC1       |remotehost3    |    30201 |        3 |DC3	  |YES		 |
ASYNC       |ACTIVE	 |               |        True |
|RH2	  |clusternode1 |30207 |xsengine     |        2 |	 1 |DC1       |remotehost3    |    30207 |        3 |DC3	  |YES		 |
ASYNC       |ACTIVE	 |               |        True |
|RH2	  |clusternode1 |30203 |indexserver  |        3 |	 1 |DC1       |remotehost3    |    30203 |        3 |DC3	  |YES		 |
ASYNC       |ACTIVE	 |               |        True |
|SYSTEMDB |clusternode1 |30201 |nameserver   |        1 |	 1 |DC1       |clusternode2    |    30201 |        2 |DC2	  |YES		 |
SYNCMEM     |ACTIVE	 |               |        True |
|RH2	  |clusternode1 |30207 |xsengine     |        2 |	 1 |DC1       |clusternode2    |    30207 |        2 |DC2	  |YES		 |
SYNCMEM     |ACTIVE	 |               |        True |
|RH2	  |clusternode1 |30203 |indexserver  |        3 |	 1 |DC1       |clusternode2    |    30203 |        2 |DC2	  |YES		 |
SYNCMEM     |ACTIVE	 |               |        True |

status system replication site "3": ACTIVE
status system replication site "2": ACTIVE
overall system replication status: ACTIVE

Local System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

mode: PRIMARY
site id: 1
site name: DC1
Status 15
Copy to Clipboard Toggle word wrap

On remotehost3 run the same command: 

remotehost3:rh2adm> watch -n 5 'python /usr/sap/$SAPSYSTEMNAME/HDB${TINSTANCE}/exe/python_support/systemReplicationStatus.py ; echo Status $?'
Copy to Clipboard Toggle word wrap

The response will be: 

this system is either not running or not primary system replication site
Copy to Clipboard Toggle word wrap

The output will change after the test initiates the failover. The output looks similar to the example of the primary node before the test was started.

On the second node start: 

clusternode2:rh2adm> watch -n 10 'hdbnsutil -sr_state | grep masters'
Copy to Clipboard Toggle word wrap

This will show the current master clusternode1 and will switch immediately after the failover is initiated.

  • To ensure that everything is configured right, please also check the global.ini.
  • Check global.ini on DC1, DC2 and DC3.

On all three nodes the global.ini should contain: 

[persistent]
log_mode=normal
[system_replication]
register_secondaries_on_takeover=true
Copy to Clipboard Toggle word wrap

You can edit the global.ini with for example: 

clusternode1:rh2adm>vim /usr/sap/$SAPSYSTEMNAME/SYS/global/hdb/custom/config/global.ini
Copy to Clipboard Toggle word wrap

  • [Optional] Put the cluster into maintenance-mode: 

    [root@clusternode1]# pcs property set maintenance-mode=true
    Copy to Clipboard Toggle word wrap

    During the tests you will find out that the failover will work with and without setting the maintenance-mode. So you can run the first test without it. While recovering it should be done, I just want to show you, it works with and without. Which is an option in terms of the primary is not accessible.

  • Start the test: Failover to DC3. On remotehost3 please run: 

    remotehost3:rh2adm> hdbnsutil -sr_takeover
done.
    Copy to Clipboard Toggle word wrap

The test has started, and now please check the output of the previously started monitors.

On the clusternode1 the system replication status will lose its relationship to remotehost3 and clusternode2 (DC2): 

Every 5.0s: python /usr/sap/RH2/HDB02/exe/python_support/systemReplicationStatus.py ; echo Status $?                               clusternode1: Mon Sep  4 11:52:16 2023

|Database |Host   |Port  |Service Name |Volume ID |Site ID |Site Name |Secondary |Secondary |Secondary |Secondary |Secondary     |Replication |Replication |Replic
ation                  |Secondary    |
|         |       |      |             |          |        |          |Host      |Port      |Site ID   |Site Name |Active Status |Mode        |Status      |Status
 Details               |Fully Synced |
|-------- |------ |----- |------------ |--------- |------- |--------- |--------- |--------- |--------- |--------- |------------- |----------- |----------- |------
---------------------- |------------ |
|SYSTEMDB |clusternode1 |30201 |nameserver   |        1 |      1 |DC1       |clusternode2    |    30201 |        2 |DC2       |YES           |SYNCMEM     |ERROR       |Commun
ication channel closed |       False |
|RH2      |clusternode1 |30207 |xsengine     |        2 |      1 |DC1       |clusternode2    |    30207 |        2 |DC2       |YES           |SYNCMEM     |ERROR       |Commun
ication channel closed |       False |
|RH2      |clusternode1 |30203 |indexserver  |        3 |      1 |DC1       |clusternode2    |    30203 |        2 |DC2       |YES           |SYNCMEM     |ERROR       |Commun
ication channel closed |       False |

status system replication site "2": ERROR
overall system replication status: ERROR

Local System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

mode: PRIMARY
site id: 1
site name: DC1
Status 11
Copy to Clipboard Toggle word wrap

The cluster still doesn’t notice this behavior. If you check the return code of the system replication status, Returncode 11 means error, which tells you something is wrong. If you have access, it is a good idea to enter maintenance-mode now.

The remotehost3 becomes the new primary and clusternode2 (DC2) gets automatically registered as the new primary on remotehost3.

Example output of the system replication state of remotehost3: 

Every 5.0s: python /usr/sap/RH2/HDB02/exe/python_support/systemReplicationStatus.py ; echo Status $?                               remotehost3: Mon Sep  4 13:55:29 2023

|Database |Host   |Port  |Service Name |Volume ID |Site ID |Site Name |Secondary |Secondary |Secondary |Secondary |Secondary     |Replication |Replication |Replic
ation    |Secondary    |
|         |       |      |             |          |        |          |Host      |Port      |Site ID   |Site Name |Active Status |Mode        |Status      |Status
 Details |Fully Synced |
|-------- |------ |----- |------------ |--------- |------- |--------- |--------- |--------- |--------- |--------- |------------- |----------- |----------- |------
-------- |------------ |
|SYSTEMDB |remotehost3 |30201 |nameserver   |        1 |      3 |DC3       |clusternode2    |    30201 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |
         |        True |
|RH2      |remotehost3 |30207 |xsengine     |        2 |      3 |DC3       |clusternode2    |    30207 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |
         |        True |
|RH2      |remotehost3 |30203 |indexserver  |        3 |      3 |DC3       |clusternode2    |    30203 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |
         |        True |

status system replication site "2": ACTIVE
overall system replication status: ACTIVE

Local System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

mode: PRIMARY
site id: 3
site name: DC3
Status 15
Copy to Clipboard Toggle word wrap

The returncode 15 also says everything is okay but clusternode1 is missing. This must be re-registered manually. The former primary clusternode1 is not listed, so the replication relationship is lost.

  • Set maintenance-mode.

If not already done before set maintenance-mode on the cluster on one node of the cluster with the command: 

[root@clusternode1]# pcs property  set maintenance-mode=true
Copy to Clipboard Toggle word wrap

You can check if the maintenance-mode is active by running this command: 

[root@clusternode1]# pcs resource
  * Clone Set: SAPHanaTopology_RH2_02-clone [SAPHanaTopology_RH2_02] (unmanaged):
    * SAPHanaTopology_RH2_02    (ocf::heartbeat:SAPHanaTopology):        Started clusternode2 (unmanaged)
    * SAPHanaTopology_RH2_02    (ocf::heartbeat:SAPHanaTopology):        Started clusternode1 (unmanaged)
  * Clone Set: SAPHana_RH2_02-clone [SAPHana_RH2_02] (promotable, unmanaged):
    * SAPHana_RH2_02    (ocf::heartbeat:SAPHana):        Slave clusternode2 (unmanaged)
    * SAPHana_RH2_02    (ocf::heartbeat:SAPHana):        Master clusternode1 (unmanaged)
  * vip_RH2_02_MASTER   (ocf::heartbeat:IPaddr2):        Started clusternode1 (unmanaged)
Copy to Clipboard Toggle word wrap

The resources are displaying unmanaged, this indicates that the cluster is in maintenance-mode=true. The virtual IP address is still started on clusternode1. If you want to use this IP on another node, please disable vip_RH2_02_MASTER before you set maintanence-mode=true. 

[root@clusternode1]# pcs resource disable vip_RH2_02_MASTER
Copy to Clipboard Toggle word wrap

  • Re-register clusternode1 When we check the sr_state on clusternode1 you will see a relationship only to DC2: 

    clusternode1:rh2adm> hdbnsutil -sr_state

System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~

online: true

mode: primary
operation mode: primary
site id: 1
site name: DC1

is source system: true
is secondary/consumer system: false
has secondaries/consumers attached: true
is a takeover active: false
is primary suspended: false

Host Mappings:
~~~~~~~~~~~~~~

clusternode1 -> [DC2] clusternode2
clusternode1 -> [DC1] clusternode1


Site Mappings:
~~~~~~~~~~~~~~
DC1 (primary/primary)
    |---DC2 (syncmem/logreplay)

Tier of DC1: 1
Tier of DC2: 2

Replication mode of DC1: primary
Replication mode of DC2: syncmem

Operation mode of DC1: primary
Operation mode of DC2: logreplay

Mapping: DC1 -> DC2
done.
    Copy to Clipboard Toggle word wrap

    But when we check DC2, the primary database server is DC3. So the information from DC1 is not correct. 

    clusternode2:rh2adm> hdbnsutil -sr_state
    Copy to Clipboard Toggle word wrap

    If we check the system replication status on DC1 the returncode is 12 which is unknown. So DC1 needs to be re-registered.

You can use this command to register the former primary clusternode1 as a new secondary of remotehost3: 

clusternode1:rh2adm> hdbnsutil -sr_register --remoteHost=remotehost3 --remoteInstance=${TINSTANCE} --replicationMode=async --name=DC1 --remoteName=DC3 --operationMode=logreplay --online
Copy to Clipboard Toggle word wrap

After the registration is done, you will see on remotehost3 all three sites replicated and the status (return code) will change to 15. If this fails, you have to manually remove the replication relationships on DC1 and DC3. Please follow the instructions described in Register Secondary. For example list the existing relations with: 

hdbnsutil -sr_state
Copy to Clipboard Toggle word wrap

Example to remove the existing relations you can use: 

clusternode1:rh2adm> hdbnsutil -sr_unregister --name=DC2
Copy to Clipboard Toggle word wrap

This may usually not be necessary.

We assume that test 4 will be performed after test 3. So the recovery step is to run test 4.

Expand

Subject of the test

Primary switch back to a cluster node.

Failback and enable the cluster again.

Re-register the third site as secondary.

Test preconditions

  • SAP HANA primary node is running on third site.
  • Cluster is partly running.
  • Cluster is put into maintenance-mode.
  • Former cluster primary is accessible.

Test steps

Check the expected primary of the cluster.

Failover from the DC3 node to the DC1 node.

Check if the former secondary has switched to the new primary.

Re-register remotehost3 as new secondary.

Set cluster maintenance-mode=false and the cluster continues to work.

Monitoring the test

On the new primary start:

remotehost3:rh2adm> watch python $DIR_EXECUTABLE/python_support/systemReplicationStatus.py [root@clusternode1]# watch pcs status --full On the secondary start: clusternode:rh2adm> watch hdbnsutil -sr_state

Starting the test

Check the expected primary of the cluster: [root@clusternode1]# pcs resource

VIP and promoted SAP HANA resources should run on the same node which is the potential new primary.

On this potential primary run: clusternode1:rh2adm> hdbnsutil -sr_takeover

Re-register the former primary as new secondary:

clusternode1:rh2adm> hdbnsutil -sr_register \ --remoteHost=clusternode1 \ --remoteInstance=${TINSTANCE} \ --replicationMode=syncmem \ --name=DC3 \ --remoteName=DC1 \ --operationMode=logreplay \ --force_full_replica \ --online

Cluster continues to work after setting the maintenance-mode=false.

Expected result

New primary is starting SAP HANA.

The replication status will show all 3 sites replicated.

Second cluster site gets automatically re-registered to the new primary.

The Disaster Recovery (DR) site becomes an additional replica of the database.

Ways to return to an initial state

Run test 3.

Detailed description

  • Check if the cluster is put into maintenance-mode: 

    [root@clusternode1]# pcs property config maintenance-mode
Cluster Properties:
 maintenance-mode: true
    Copy to Clipboard Toggle word wrap

    If the maintenance-mode is not true you can set it with: 

    [root@clusternode1]# pcs property set  maintenance-mode=true
    Copy to Clipboard Toggle word wrap

  • Check system replication status and discover the primary database on all nodes. First of all discover the primary database using: 

    clusternode1:rh2adm> hdbnsutil -sr_state | egrep -e "^mode:|primary masters"
    Copy to Clipboard Toggle word wrap

The output should be as follows.

On clusternode1: 

clusternode1:rh2adm> hdbnsutil -sr_state | egrep -e "^mode:|primary masters"
mode: syncmem
primary masters: remotehost3
Copy to Clipboard Toggle word wrap

On clusternode2: 

clusternode2:rh2adm> hdbnsutil -sr_state | egrep -e "^mode:|primary masters"
mode: syncmem
primary masters: remotehost3
Copy to Clipboard Toggle word wrap

On remotehost3: 

remotehost3:rh2adm> hdbnsutil -sr_state | egrep -e "^mode:|primary masters"
mode: primary
Copy to Clipboard Toggle word wrap

On all three nodes the primary database is remotehost3. On this primary database, you have to ensure, that the system replication status is active for all three nodes and the return code is 15: 

remotehost3:rh2adm> python /usr/sap/$SAPSYSTEMNAME/HDB${TINSTANCE}/exe/python_support/systemReplicationStatus.py
|Database |Host   |Port  |Service Name |Volume ID |Site ID |Site Name |Secondary |Secondary |Secondary |Secondary |Secondary     |Replication |Replication |Replication    |Secondary    |
|         |       |      |             |          |        |          |Host      |Port      |Site ID   |Site Name |Active Status |Mode        |Status      |Status Details |Fully Synced |
|-------- |------ |----- |------------ |--------- |------- |--------- |--------- |--------- |--------- |--------- |------------- |----------- |----------- |-------------- |------------ |
|SYSTEMDB |remotehost3 |30201 |nameserver   |        1 |      3 |DC3       |clusternode2    |    30201 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |remotehost3 |30207 |xsengine     |        2 |      3 |DC3       |clusternode2    |    30207 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |remotehost3 |30203 |indexserver  |        3 |      3 |DC3       |clusternode2    |    30203 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|SYSTEMDB |remotehost3 |30201 |nameserver   |        1 |      3 |DC3       |clusternode1    |    30201 |        1 |DC1       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |remotehost3 |30207 |xsengine     |        2 |      3 |DC3       |clusternode1    |    30207 |        1 |DC1       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |remotehost3 |30203 |indexserver  |        3 |      3 |DC3       |clusternode1    |    30203 |        1 |DC1       |YES           |SYNCMEM     |ACTIVE      |               |        True |

status system replication site "2": ACTIVE
status system replication site "1": ACTIVE
overall system replication status: ACTIVE

Local System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

mode: PRIMARY
site id: 3
site name: DC3
[rh2adm@remotehost3: python_support]# echo $?
15
Copy to Clipboard Toggle word wrap
  • Check all three sr_states are consistent.

Please run on all three nodes hdbnsutil -sr_state --sapcontrol=1 |grep site.*Mode: 

clusternode1:rh2adm>hdbnsutil -sr_state --sapcontrol=1 |grep  site.*Mode
Copy to Clipboard Toggle word wrap 
clusternode2:rh2adm>hsbnsutil -sr_state --sapcontrol=1 | grep site.*Mode
Copy to Clipboard Toggle word wrap 
remotehost3:rh2adm>hsbnsutil -sr_state --sapcontrol=1 | grep site.*Mode
Copy to Clipboard Toggle word wrap

The output should be the same on all nodes: 

siteReplicationMode/DC1=primary
siteReplicationMode/DC3=async
siteReplicationMode/DC2=syncmem
siteOperationMode/DC1=primary
siteOperationMode/DC3=logreplay
siteOperationMode/DC2=logreplay
Copy to Clipboard Toggle word wrap
  • Start the monitoring in separate windows.

On clusternode1 start: 

clusternode1:rh2adm> watch "python /usr/sap/$SAPSYSTEMNAME/HDB${TINSTANCE}/exe/python_support/systemReplicationStatus.py; echo \$?"
Copy to Clipboard Toggle word wrap

On remotehost3 start: 

remotehost3:rh2adm> watch "python /usr/sap/$SAPSYSTEMNAME/HDB${TINSTANCE}/exe/python_support/systemReplicationStatus.py; echo \$?"
Copy to Clipboard Toggle word wrap

On clusternode2 start: 

clusternode2:rh2adm> watch "hdbnsutil -sr_state --sapcontrol=1 |grep  siteReplicationMode"
Copy to Clipboard Toggle word wrap
  • Start the test

To failover to clusternode1 start on clusternode1: 

clusternode1:rh2adm> hdbnsutil -sr_takeover
done.
Copy to Clipboard Toggle word wrap
  • Check the output of the monitors.

The monitor on clusternode1 will change to: 

Every 2.0s: python systemReplicationStatus.py; echo $?                                                                                                                                                            clusternode1: Mon Sep  4 23:34:30 2023

|Database |Host   |Port  |Service Name |Volume ID |Site ID |Site Name |Secondary |Secondary |Secondary |Secondary |Secondary     |Replication |Replication |Replication    |Secondary    |
|         |       |      |             |          |        |          |Host      |Port      |Site ID   |Site Name |Active Status |Mode        |Status      |Status Details |Fully Synced |
|-------- |------ |----- |------------ |--------- |------- |--------- |--------- |--------- |--------- |--------- |------------- |----------- |----------- |-------------- |------------ |
|SYSTEMDB |clusternode1 |30201 |nameserver   |        1 |      1 |DC1       |clusternode2    |    30201 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |clusternode1 |30207 |xsengine     |        2 |      1 |DC1       |clusternode2    |    30207 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |clusternode1 |30203 |indexserver  |        3 |      1 |DC1       |clusternode2    |    30203 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |

status system replication site "2": ACTIVE
overall system replication status: ACTIVE

Local System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

mode: PRIMARY
site id: 1
site name: DC1
15
Copy to Clipboard Toggle word wrap

Important is also the return code 15. The monitor on clusternode2 will change to: 

Every 2.0s: hdbnsutil -sr_state --sapcontrol=1 |grep  site.*Mode                                                                clusternode2: Mon Sep  4 23:35:18 2023

siteReplicationMode/DC1=primary
siteReplicationMode/DC2=syncmem
siteOperationMode/DC1=primary
siteOperationMode/DC2=logreplay
Copy to Clipboard Toggle word wrap

DC3 is gone and needs to be re-registered. On remotehost3 the systemReplicationStatus reports an error and the returncode changes to 11.

  • Check if cluster nodes gets re-registered. 

    clusternode1:rh2adm>  hdbnsutil -sr_state

System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~

online: true

mode: primary
operation mode: primary
site id: 1
site name: DC1

is source system: true
is secondary/consumer system: false
has secondaries/consumers attached: true
is a takeover active: false
is primary suspended: false

Host Mappings:
~~~~~~~~~~~~~~

clusternode1 -> [DC2] clusternode2
clusternode1 -> [DC1] clusternode1


Site Mappings:
~~~~~~~~~~~~~~
DC1 (primary/primary)
    |---DC2 (syncmem/logreplay)

Tier of DC1: 1
Tier of DC2: 2

Replication mode of DC1: primary
Replication mode of DC2: syncmem

Operation mode of DC1: primary
Operation mode of DC2: logreplay

Mapping: DC1 -> DC2
done.
    Copy to Clipboard Toggle word wrap

    The Site Mappings shows, clusternode2 (DC2) was re-registered.

  • Check or enable the vip resource: 

    [root@clusternode1]# pcs resource
  * Clone Set: SAPHanaTopology_RH2_02-clone [SAPHanaTopology_RH2_02] (unmanaged):
    * SAPHanaTopology_RH2_02    (ocf::heartbeat:SAPHanaTopology):        Started clusternode2 (unmanaged)
    * SAPHanaTopology_RH2_02    (ocf::heartbeat:SAPHanaTopology):        Started clusternode1
   (unmanaged)
  * Clone Set: SAPHana_RH2_02-clone [SAPHana_RH2_02] (promotable, unmanaged):
    * SAPHana_RH2_02    (ocf::heartbeat:SAPHana):        Master clusternode2 (unmanaged)
    * SAPHana_RH2_02    (ocf::heartbeat:SAPHana):        Slave clusternode1
   (unmanaged)
  * vip_RH2_02_MASTER   (ocf::heartbeat:IPaddr2):        Stopped (disabled, unmanaged)
    Copy to Clipboard Toggle word wrap

    The vip resource vip_RH2_02_MASTER is stopped. To start it again run: 

[root@clusternode1]# pcs resource enable vip_RH2_02_MASTER
Warning: 'vip_RH2_02_MASTER' is unmanaged
Copy to Clipboard Toggle word wrap

The warning is right, because the cluster will not start any resource unless maintenance-mode=false.

  • Stop cluster maintenance-mode.

Before we stop the maintenance-mode we should start two monitors in separate windows to see the changes. On clusternode2 run: 

[root@clusternode2]# watch pcs status --full
Copy to Clipboard Toggle word wrap

On clusternode1 run: 

clusternode1:rh2adm> watch "python /usr/sap/$SAPSYSTEMNAME/HDB${TINSTANCE}/exe/python_support/systemReplicationStatus.py; echo $?"
Copy to Clipboard Toggle word wrap

Now you can unset the maintenance-mode on clusternode1 by running: 

[root@clusternode1]# pcs property set maintenance-mode=false
Copy to Clipboard Toggle word wrap

The monitor on clusternode2 should show you that everything is running now as expected: 

Every 2.0s: pcs status --full                                                                                                                                                                                     clusternode1: Tue Sep  5 00:01:17 2023

Cluster name: cluster1
Cluster Summary:
  * Stack: corosync
  * Current DC: clusternode1
 (1) (version 2.1.2-4.el8_6.6-ada5c3b36e2) - partition with quorum
  * Last updated: Tue Sep  5 00:01:17 2023
  * Last change:  Tue Sep  5 00:00:30 2023 by root via crm_attribute on clusternode1

  * 2 nodes configured
  * 6 resource instances configured

Node List:
  * Online: [ clusternode1
 (1) clusternode2 (2) ]

Full List of Resources:
  * auto_rhevm_fence1   (stonith:fence_rhevm):   Started clusternode1

  * Clone Set: SAPHanaTopology_RH2_02-clone [SAPHanaTopology_RH2_02]:
    * SAPHanaTopology_RH2_02    (ocf::heartbeat:SAPHanaTopology):        Started clusternode2
    * SAPHanaTopology_RH2_02    (ocf::heartbeat:SAPHanaTopology):        Started clusternode1

  * Clone Set: SAPHana_RH2_02-clone [SAPHana_RH2_02] (promotable):
    * SAPHana_RH2_02    (ocf::heartbeat:SAPHana):        Slave clusternode2
    * SAPHana_RH2_02    (ocf::heartbeat:SAPHana):        Master clusternode1

  * vip_RH2_02_MASTER   (ocf::heartbeat:IPaddr2):        Started clusternode1


Node Attributes:
  * Node: clusternode1
 (1):
    * hana_rh2_clone_state              : PROMOTED
    * hana_rh2_op_mode                  : logreplay
    * hana_rh2_remoteHost               : clusternode2
    * hana_rh2_roles                    : 4:P:master1:master:worker:master
    * hana_rh2_site                     : DC1
    * hana_rh2_sra                      : -
    * hana_rh2_srah                     : -
    * hana_rh2_srmode                   : syncmem
    * hana_rh2_sync_state               : PRIM
    * hana_rh2_version                  : 2.00.062.00
    * hana_rh2_vhost                    : clusternode1

    * lpa_rh2_lpt                       : 1693872030
    * master-SAPHana_RH2_02             : 150
  * Node: clusternode2 (2):
    * hana_rh2_clone_state              : DEMOTED
    * hana_rh2_op_mode                  : logreplay
    * hana_rh2_remoteHost               : clusternode1

    * hana_rh2_roles                    : 4:S:master1:master:worker:master
    * hana_rh2_site                     : DC2
    * hana_rh2_sra                      : -
    * hana_rh2_srah                     : -
    * hana_rh2_srmode                   : syncmem
    * hana_rh2_sync_state               : SOK
    * hana_rh2_version                  : 2.00.062.00
    * hana_rh2_vhost                    : clusternode2
    * lpa_rh2_lpt                       : 30
    * master-SAPHana_RH2_02             : 100

Migration Summary:

Tickets:

PCSD Status:
  clusternode1
: Online
  clusternode2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled
Copy to Clipboard Toggle word wrap

After manual interaction it is always a good advice to cleanup the cluster like described in Cluster Cleanup.

  • Re-register remotehost3 to the new primary on clusternode1.

Remotehost3 needs to be re-registered. To monitor the progress please start on clusternode1: 

clusternode1:rh2adm> watch -n 5 'python
/usr/sap/$SAPSYSTEMNAME/HDB${TINSTANCE}/exe/python_support/systemReplicationStatus.py ; echo Status $?'
Copy to Clipboard Toggle word wrap

On remotehost3 please start: 

remotehost3:rh2adm> watch 'hdbnsutil -sr_state --sapcontrol=1 |grep  siteReplicationMode'
Copy to Clipboard Toggle word wrap

Now you can re-register remotehost3 with this command: 

remotehost3:rh2adm> hdbnsutil -sr_register --remoteHost=clusternode1 --remoteInstance=${TINSTANCE} --replicationMode=async --name=DC3 --remoteName=DC1 --operationMode=logreplay --online
Copy to Clipboard Toggle word wrap

The monitor on clusternode1 will change to: 

Every 5.0s: python /usr/sap/$SAPSYSTEMNAME/HDB${TINSTANCE}/exe/python_support/systemReplicationStatus.py ; echo Status $?                                                                                         clusternode1: Tue Sep  5 00:14:40 2023

|Database |Host   |Port  |Service Name |Volume ID |Site ID |Site Name |Secondary |Secondary |Secondary |Secondary |Secondary     |Replication |Replication |Replication    |Secondary    |
|         |       |      |             |          |        |          |Host      |Port      |Site ID   |Site Name |Active Status |Mode        |Status      |Status Details |Fully Synced |
|-------- |------ |----- |------------ |--------- |------- |--------- |--------- |--------- |--------- |--------- |------------- |----------- |----------- |-------------- |------------ |
|SYSTEMDB |clusternode1 |30201 |nameserver   |        1 |      1 |DC1       |remotehost3    |    30201 |        3 |DC3       |YES           |ASYNC     |ACTIVE      |               |        True |
|RH2      |clusternode1 |30207 |xsengine     |        2 |      1 |DC1       |remotehost3    |    30207 |        3 |DC3       |YES           |ASYNC     |ACTIVE      |               |        True |
|RH2      |clusternode1 |30203 |indexserver  |        3 |      1 |DC1       |remotehost3    |    30203 |        3 |DC3       |YES           |ASYNC     |ACTIVE      |               |        True |
|SYSTEMDB |clusternode1 |30201 |nameserver   |        1 |      1 |DC1       |clusternode2    |    30201 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |clusternode1 |30207 |xsengine     |        2 |      1 |DC1       |clusternode2    |    30207 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |
|RH2      |clusternode1 |30203 |indexserver  |        3 |      1 |DC1       |clusternode2    |    30203 |        2 |DC2       |YES           |SYNCMEM     |ACTIVE      |               |        True |

status system replication site "3": ACTIVE
status system replication site "2": ACTIVE
overall system replication status: ACTIVE

Local System Replication State
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

mode: PRIMARY
site id: 1
site name: DC1
Status 15
Copy to Clipboard Toggle word wrap

And the monitor of remotehost3 will change to: 

Every 2.0s: hdbnsutil -sr_state --sapcontrol=1 |grep  site.*Mode                                                                remotehost3: Tue Sep  5 02:15:28 2023

siteReplicationMode/DC1=primary
siteReplicationMode/DC3=syncmem
siteReplicationMode/DC2=syncmem
siteOperationMode/DC1=primary
siteOperationMode/DC3=logreplay
siteOperationMode/DC2=logreplay
Copy to Clipboard Toggle word wrap

Now we have again 3 entries and remotehost3 (DC3) is again a secondary site replicated from clusternode1 (DC1).

  • Check if all nodes are part of the system replication status on clusternode1.

Please run on all three nodes hdbnsutil -sr_state --sapcontrol=1 |grep site.*Mode: 

clusternode1:rh2adm> hdbnsutil -sr_state --sapcontrol=1 |grep  site.*ModesiteReplicationMode
Copy to Clipboard Toggle word wrap 
clusternode2:rh2adm> hsbnsutil -sr_state --sapcontrol=1 | grep site.*Mode
Copy to Clipboard Toggle word wrap 
remotehost3:rh2adm> hsbnsutil -sr_state --sapcontrol=1 | grep site.*Mode
Copy to Clipboard Toggle word wrap

On all nodes we should get the same output: 

siteReplicationMode/DC1=primary
siteReplicationMode/DC3=syncmem
siteReplicationMode/DC2=syncmem
siteOperationMode/DC1=primary
siteOperationMode/DC3=logreplay
siteOperationMode/DC2=logreplay
Copy to Clipboard Toggle word wrap
  • Check pcs status --full and SOK. Run: 
[root@clusternode1]# pcs status --full| grep sync_state
Copy to Clipboard Toggle word wrap

The output should be either PRIM or SOK: 

 * hana_rh2_sync_state             	: PRIM
    * hana_rh2_sync_state             	: SOK
Copy to Clipboard Toggle word wrap

Finally the cluster status should look like this including the sync_state PRIM and SOK: 

[root@clusternode1]# pcs status --full
Cluster name: cluster1
Cluster Summary:
  * Stack: corosync
  * Current DC: clusternode1
 (1) (version 2.1.2-4.el8_6.6-ada5c3b36e2) - partition with quorum
  * Last updated: Tue Sep  5 00:18:52 2023
  * Last change:  Tue Sep  5 00:16:54 2023 by root via crm_attribute on clusternode1

  * 2 nodes configured
  * 6 resource instances configured

Node List:
  * Online: [ clusternode1
 (1) clusternode2 (2) ]

Full List of Resources:
  * auto_rhevm_fence1   (stonith:fence_rhevm):   Started clusternode1

  * Clone Set: SAPHanaTopology_RH2_02-clone [SAPHanaTopology_RH2_02]:
    * SAPHanaTopology_RH2_02    (ocf::heartbeat:SAPHanaTopology):        Started clusternode2
    * SAPHanaTopology_RH2_02    (ocf::heartbeat:SAPHanaTopology):        Started clusternode1

  * Clone Set: SAPHana_RH2_02-clone [SAPHana_RH2_02] (promotable):
    * SAPHana_RH2_02    (ocf::heartbeat:SAPHana):        Slave clusternode2
    * SAPHana_RH2_02    (ocf::heartbeat:SAPHana):        Master clusternode1

  * vip_RH2_02_MASTER   (ocf::heartbeat:IPaddr2):        Started clusternode1


Node Attributes:
  * Node: clusternode1
 (1):
    * hana_rh2_clone_state              : PROMOTED
    * hana_rh2_op_mode                  : logreplay
    * hana_rh2_remoteHost               : clusternode2
    * hana_rh2_roles                    : 4:P:master1:master:worker:master
    * hana_rh2_site                     : DC1
    * hana_rh2_sra                      : -
    * hana_rh2_srah                     : -
    * hana_rh2_srmode                   : syncmem
    * hana_rh2_sync_state               : PRIM
    * hana_rh2_version                  : 2.00.062.00
    * hana_rh2_vhost                    : clusternode1

    * lpa_rh2_lpt                       : 1693873014
    * master-SAPHana_RH2_02             : 150
  * Node: clusternode2 (2):
    * hana_rh2_clone_state              : DEMOTED
    * hana_rh2_op_mode                  : logreplay
    * hana_rh2_remoteHost               : clusternode1

    * hana_rh2_roles                    : 4:S:master1:master:worker:master
    * hana_rh2_site                     : DC2
    * hana_rh2_sra                      : -
    * hana_rh2_srah                     : -
    * hana_rh2_srmode                   : syncmem
    * hana_rh2_sync_state               : SOK
    * hana_rh2_version                  : 2.00.062.00
    * hana_rh2_vhost                    : clusternode2
    * lpa_rh2_lpt                       : 30
    * master-SAPHana_RH2_02             : 100

Migration Summary:

Tickets:

PCSD Status:
  clusternode1
: Online
  clusternode2: Online

Daemon Status:
  corosync: active/disabled
  pacemaker: active/disabled
  pcsd: active/enabled
Copy to Clipboard Toggle word wrap

Refer to Check cluster status and Check database, to verify that all works fine again.

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