OracleLinux6.1 installation Oracle10gORA-27125: unabletocreatesha

Installing Oracle10.2.0.1 on OracleLinux6.1 is a tortuous process during software installation. When dbca creates an instance, it encounters:

Installing Oracle 10.2.0.1 on Oracle Linux 6.1 is a tortuous process when installing software. When dbca creates an instance, it encounters:

Installing Oracle 10.2.0.1 on Oracle Linux 6.1 is a tortuous process when installing software. When dbca creates an instance, it encounters:

ORA-27125: unable to create shared memory segment

The installation is interrupted.

Rac2:/u02> oerr ora 27125

27125,000 00, "unable to create sharedmemory segment"

// * Cause: shmget () call failed

// * Action: contact Oracle support

The solution is as follows:

[Root @ rac2 ~] # Id oracle

Uid = 500 (oracle) gid = 501 (oinstall) groups = 501 (oinstall), 502 (dba), 503 (asmadmin), 504 (region)

[Root @ rac2 ~] # More/proc/sys/vm/hugetlb_shm_group

0

Run the following command as root to add the dba group to the system kernel:

[Root @ rac2 ~] # Echo 502>/proc/sys/vm/hugetlb_shm_group

-- Here 502 is shown by the id command above.

[Root @ rac2 ~] # More/proc/sys/vm/hugetlb_shm_group

502

Then, run DBCA again to create an instance. If an Instance name already exists, delete the corresponding records in/etc/oratab.

Hugetlb_shm_group description:

Hugetlb_shm_group contains group id that isallowed to create SysV shared memory segment using hugetlb page

When a process uses some memory, the CPU ismarking the RAM as used by that process. for efficiency, the CPU allocate RAMby chunks of 4 K bytes (it's the default value on your platforms ). those chunksare named pages. those pages can be swapped to disk, etc.

Since the process address space are virtual, the CPU and the operating systemhave to remember which page belong to which process, and where it is stored. obviusly, the more pages you have, the more time it takes to find where thememory is mapped. when a process uses 1 GB of memory, that's 262144 entries to lookup (1 GB/4 K ). if one Page Table Entry consume 8 bytes, that's 2 MB (262144*8) to look-up.

Most current CPU ubuntures support bigger pages (so the CPU/OS have lessentries to look-up), those are named Huge pages (on Linux), Super Pages (onBSD) or Large Pages (on Windows), but it all the same thing.