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Chapter 5. Test cases

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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 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 names 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

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 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

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:

  • pcs status | grep -E "Promoted|Master"
  • hdbnsutil -sr_stateConfiguration

Check if there is enough space on the file systems by running: 

# df -h

Please also follow the guidelines for a system check before you continue. If the environment is clean, it is ready to run the tests. During the test, monitoring is helpful to observe progress.

5.2. Monitor the environment

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 the monitors from a dedicated terminal. 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

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"'

Output example, when clusternode2 is the primary database: 

mode: syncmem
primary masters: clusternode2

A second way to identify the primary node is to run the following command as root on a cluster node: 

# watch -n 5 'pcs status --full'

Output on the node that runs the primary database is: 

mode: primary

5.2.2. Check the Replication status

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

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 $?'

This example repeatedly captures the replication status and 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

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 message file on a single cluster node.

For example, you can use this alias: 

# 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"'

Run this alias 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

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. 

# pcs status --full

If you want to see changes, you can run, in a separate window, the command watch: 

# watch pcs status --full

An output example and further options can be found in Check cluster status.

5.2.5. Discover leftovers

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: clusternode1:rh2adm> 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_EXECUTABLES}/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.

5.3. Test 1:Failover of the primary node with an active third site

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

Monitoring the test

On the third site run as sidadm 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

[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’

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

    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 the changes. 

    [root@clusternode1]# watch pcs status --full

  • 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 ]

    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"

    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

    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

    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

    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

    This constraint needs to be removed by executing the following steps.

  • 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

  • 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)

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-registered, 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 Cluster Cleanup.

5.4. Test 2:Failover of the primary node with passive third site

Subject of the test

No registration of the 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 move command.

Starting the test

Execute the cluster command:

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

Monitoring the test

On the third site run as sidadm: % watch hdbnsutil -sr_stateConfiguration

On the cluster nodes run as root: [root@clusternode1]# watch pcs status

Expected result

No change on DC3. 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

    This 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, it 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.

  • Check the primary database on remotehost3: 

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

primary masters: clusternode2

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

    [root@clusternode1]# pcs resource | grep Masters
    * Masters: [ clusternode2 ]

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

    clusternode2remotehost3: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.

    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.

    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
    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 displayed with: 

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

    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

  • 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)

  • 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: 

    remotehost3clusternode2:rh2adm>  hdbnsutil -sr_stateConfiguration| grep -i primary
active primary site: 1
primary masters: clusternode1

    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 ]

    Here we have an inconsistency, which requires us to re-register remotehost3. You might think that 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 run: 

    clusternode2:rh2adm> cdpy
clusternode2:rh2adm> python ${DIR_EXECUTABLES}/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

    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_EXECUTABLES}/python_support/systemReplicationStatus.py

    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.

    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

    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.
  • The missing entry will be immediately created, and the system replication will start as soon as the SAP HANA database is started.

  • You can check this by executing: 

    sidadm@clusternode1% hdbnsutil -sr_state
sidadm@clusternode1% python systemReplicationStatus.py ; echo $?
  • You can find more information in Check SAP HANA System Replication status.

5.5. Test 3:Failover of the primary node to the third site

Subject of the test

Failover the primary to the third site.. Third site becomes primary.

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: % hdbnsuttil -sr_takeover

Starting the test

Execute the SAP HANA command on remotehost3:rh2adm>: hdbnsutil -sr_takeover

Monitoring the test

On the third site run as sidadm% 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"

    The output is, for example: 

    mode: syncmem
primary masters: clusternode1

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

    mode: primary

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

    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

  • 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 $?'

    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

    On remotehost3, run the same command: 

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

    The response will be: 

    this system is either not running or is not primary system replication site

    This 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'

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

  • To ensure that everything is configured correctly, 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

    You can edit the global.ini with: 

    clusternode1:rh2adm>vim /usr/sap/${SAPSYSTEMNAME}/SYS/global/hdb/custom/config/global.ini

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

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

    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 that it works with and without. This is an option if the primary is not accessible.

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

    remotehost3:rh2adm> hdbnsutil -sr_takeover
done.

    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

    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 the 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

    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

    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 clusternode2node2 (unmanaged)
    * SAPHanaTopology_RH2_02    (ocf::heartbeat:SAPHanaTopology):        Started clusternode1node1 (unmanaged)
  * Clone Set: SAPHana_RH2_02-clone [SAPHana_RH2_02] (promotable, unmanaged):
    * SAPHana_RH2_02    (ocf::heartbeat:SAPHana):        Slave clusternode2node2 (unmanaged)
    * SAPHana_RH2_02    (ocf::heartbeat:SAPHana):        Master clusternode1node1 (unmanaged)
  * vip_RH2_02_MASTER   (ocf::heartbeat:IPaddr2):        Started clusternode1node1 (unmanaged)

    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

  • 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.

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

    clusternode2:rh2adm> hdbnsutil -sr_state

    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=asyncsyncmem --name=DC1 --remoteName=DC3 --operationMode=logreplay --online

    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 relationships with: 

    clusternode1:rh2adm> hdbnsutil -sr_state

    To remove the existing relationships you can use: 

    clusternode1:rh2adm> hdbnsutil -sr_unregister --name=DC2`

    This may not usually be necessary. We assume that test 4 will be performed after test 3. So the recovery step is to run test 4.

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

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 detectable.

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 a 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_EXECUTABLES}/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 as sidadm: 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.

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

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

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

  • Check the 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"

    The output should be as follows:

    On clusternode1: 

    clusternode1:rh2adm> hdbnsutil -sr_state | egrep -e "^mode:|primary masters"
mode: syncmem
primary masters: remotehost3

    On clusternode2: 

    clusternode2:rh2adm> hdbnsutil -sr_state | egrep -e "^mode:|primary masters"
mode: syncmem
primary masters: remotehost3

    On remotehost3: 

    remotehost3:rh2adm> hdbnsutil -sr_state | egrep -e "^mode:|primary masters"
mode: primary

    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

  • Check if 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


clusternode2:rh2adm> hsbnsutil -sr_state --sapcontrol=1 | grep site.*Mode


remotehost3:rh2adm>hsbnsutil -sr_state --sapcontrol=1 | grep site.*Mode

    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

  • Start monitoring in separate windows.

    On clusternode1, start: 

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

    On remotehost3, start: 

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

    On clusternode2, start: 

    clusternode2:rh2adm> watch "hdbnsutil -sr_state --sapcontrol=1 |grep  siteReplicationMode"

  • Start the test.

    To failover to clusternode1, start on clusternode1: 

    clusternode1:rh2adm> hdbnsutil -sr_takeover
done.

  • 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

    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

    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 get 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.

    The Site Mapping shows that 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)

    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

    The warning is right because the cluster will not start any resources 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

    On clusternode1, run: 

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

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

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

    The monitor on clusternode1 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

    After manual interaction, it is always good advice to cleanup the cluster, as 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: 

    con_cluster_cleanupclusternode1:rh2adm> watch -n 5 'python /usr/sap/${SAPSYSTEMNAME}/HDB${TINSTANCE}/exe/python_support/systemReplicationStatus.py ; echo Status $?'

    On remotehost3, please start: 

    remotehost3:rh2adm> watch 'hdbnsutil -sr_state --sapcontrol=1 |grep  siteReplicationMode'

    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

    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

    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

    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


clusternode2:rh2adm> hsbnsutil -sr_state --sapcontrol=1 | grep site.*Mode


remotehost3:rh2adm> hsbnsutil -sr_state --sapcontrol=1 | grep site.*Mode

    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

  • Check pcs status --full and SOK.

    Run: 

    [root@clusternode1]# pcs status --full| grep sync_state

    The output should be either PRIM or SOK: 

     * hana_rh2_sync_state             	: PRIM
    * hana_rh2_sync_state             	: SOK

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