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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
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Make the script executable: 
# chown root.root /usr/local/bin/ChangeMappedBase
# chmod 755 /usr/local/bin/ChangeMappedBase
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Allow the oracle user to execute /usr/local/bin/ChangeMappedBase via sudo without password: 
# echo "oracle   ALL=NOPASSWD: /usr/local/bin/ChangeMappedBase" >> \
	/etc/sudoers
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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$
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To change the mapping for shared libraries automatically during the Oracle log in process, execute: 
# echo "sudo /usr/local/bin/ChangeMappedBase" >> ~/.bash_profile
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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$
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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>
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