Red Hat ENTERPRISE LINUX AS 2.1 - Installationsanleitung PDF herunterladen (Seite 23)

Removing Shared Memory

system is 2097152*4096 bytes (shmall*PAGE_SIZE) which is 8 GB. PAGE_SIZE is usually 4096

bytes unless you use Chapter 14, Large Memory Optimization, Big Pages, and Huge Pages which

supports the configuration of larger memory pages.

If you are not sure what the default PAGE_SIZE is on your Linux system, you can run the following

command:

$ getconf PAGE_SIZE

4096

To determine the system wide maximum number of shared memory pages, run:

# cat /proc/sys/kernel/shmall

2097152

The default shared memory limit for SHMALL can be changed in the proc file system without reboot:

# echo 2097152 > /proc/sys/kernel/shmall

Alternatively, you can use sysctl(8) to change it:

# sysctl -w kernel.shmall=2097152

To make the change permanent, add the following line to the file /etc/sysctl.conf. This file is

used during the boot process.

# echo "kernel.shmall=2097152" >> /etc/sysctl.conf

7.4. Removing Shared Memory

Sometimes after an instance crash you may have to remove Oracle's shared memory segments

manually.

To see all shared memory segments that are allocated on the system, execute:

$ ipcs -m

------ Shared Memory Segments --------

key shmid owner perms bytes nattch status

0x8f6e2129 98305 oracle 600 77694523 0

0x2f629238 65536 oracle 640 2736783360 35

0x00000000 32768 oracle 640 2736783360 0 dest

In this example you can see that three shared memory segments have been allocated. The output

also shows that shmid 32768 is an abandoned shared memory segment from a past ungraceful Oracle

shutdown. Status "dest" means that this memory segment is marked to be destroyed. To find out

more about this shared memory segment you can run:

$ ipcs -m -i 32768

Shared memory Segment shmid=32768

uid=500 gid=501 cuid=500 cgid=501

mode=0640 access_perms=0640

1 2 ... 18 19 20 21 22 23 24 25 26 27 28 ... 159 160

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Red Hat ENTERPRISE LINUX AS 2.1 - Installationsanleitung Seite 23