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15.6. Allowing the Oracle User to Change the Mapped Base Address for Shared Libraries
As shown at Section 15.4, “Lowering the Mapped Base Address for Shared Libraries in Red Hat Enterprise Linux 2.1” only root can change the mapped_base for shared libraries. Using sudo we can give the "oracle" user the privilege to change the mapped base for shared libraries for the shell terminal session without providing full root access to the system.
The procedure is as follows:
Create a script called "
/usr/local/bin/ChangeMappedBase" which changes the mapped_base for shared libraries for for its own shell:
cat /usr/local/bin/ChangeMappedBase #/bin/sh echo 268435456 > /proc/$PPID/mapped_base
# cat /usr/local/bin/ChangeMappedBase
#/bin/sh
echo 268435456 > /proc/$PPID/mapped_base
Make the script executable:
chown root.root /usr/local/bin/ChangeMappedBase chmod 755 /usr/local/bin/ChangeMappedBase
# chown root.root /usr/local/bin/ChangeMappedBase
# chmod 755 /usr/local/bin/ChangeMappedBase
Allow the oracle user to execute
/usr/local/bin/ChangeMappedBase via sudo without password:
echo "oracle ALL=NOPASSWD: /usr/local/bin/ChangeMappedBase" >> \ /etc/sudoers
# echo "oracle ALL=NOPASSWD: /usr/local/bin/ChangeMappedBase" >> \
/etc/sudoers
Now the Oracle user can run
/usr/local/bin/ChangeMappedBase to change the mapped_base for its own shell:
su - oracle cat /proc/$$/mapped_base; echo 1073741824 sudo /usr/local/bin/ChangeMappedBase cat /proc/$$/mapped_base; echo 268435456$
$ su - oracle
$ cat /proc/$$/mapped_base; echo
1073741824
$ sudo /usr/local/bin/ChangeMappedBase
$ cat /proc/$$/mapped_base; echo
268435456$
To change the mapping for shared libraries automatically during the Oracle log in process, execute:
echo "sudo /usr/local/bin/ChangeMappedBase" >> ~/.bash_profile
# echo "sudo /usr/local/bin/ChangeMappedBase" >> ~/.bash_profile
Now log in as
oracle:
ssh oracle@localhost oracle@localhost's password: Last login: Sun Jan 7 13:59:22 2003 from localhost cat /proc/$$/mapped_base; echo 268435456$
$ ssh oracle@localhost
oracle@localhost's password:
Last login: Sun Jan 7 13:59:22 2003 from localhost
$ cat /proc/$$/mapped_base; echo
268435456$Note
If the mapped base address for shared libraries for the Oracle processes was changed, then every Linux shell that spawns Oracle processes (for example,
listener, sqlplus, etc.) must have the same mapped base address as well. If you execute sqlplus to connect to the local database, then you will get the following error message, seen in the screen below, if the mapped_base for this shell is not the same as for the running Oracle processes.
SQL> connect scott/tiger ERROR: ORA-01034: ORACLE not available ORA-27102: out of memory Linux Error: 12: Cannot allocate memory Additional information: 1 Additional information: 491524 SQL>
SQL> connect scott/tiger
ERROR:
ORA-01034: ORACLE not available
ORA-27102: out of memory
Linux Error: 12: Cannot allocate memory
Additional information: 1
Additional information: 491524
SQL>
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