Setting shared memory options

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You can use shared memory communications between clients and servers on the same system. To use shared memory, TCP/IP Version 4 must be installed on the system.

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The following example shows a shared memory setting:

commmethod     sharedmem
   shmport     1510

In this example, SHMPORT specifies the TCP/IP port address of a server when using shared memory. Use the SHMPORT option to specify a different TCP/IP port. The default port address is 1510.

COMMMETHOD can be used multiple times in the IBM Storage Protect server options file, with a different value each time. For example, the following example is possible:

commmethod tcpip
commmethod sharedmem

AIX operating systems The maximum number of concurrent shared memory sessions is based on available system resources. Each shared memory session uses one shared memory region of up to 4 MB, and four IPCS message queues, depending on the IBM Storage Protect client level.

AIX operating systems If the server and client are not run under the same user ID, then the server must be root. This prevents shared memory communication errors.

You might receive the following message from the server when using shared memory:

ANR9999D shmcomm.c(1598): ThreadId<39>
Error from msgget (2), errno = 28

The message means that a message queue must be created but the system limit for the maximum number of message queues (MSGMNI) would be exceeded.

To find out the maximum number of message queues (MSGMNI) on your system, issue the following command:

cat /proc/sys/kernel/msgmni

To increase the MSGMNI value on your system, issue the following command:

sysctl -w kernel.msgmni=n

where n is the maximum number of message queues that you want the system to allow.