Adjusting Pool Sizes

Use

Many of the SAP buffers are contained in shared memory pools. When the sizes of these buffers are changed, it is necessary to adjust the size of the corresponding pool as well.

The CCMS profile maintenance tool makes these adjustments automatically.

Procedure

To display information about the shared memory segments and the pools, from the initial screen, choose Tools → Administration → Monitor → Performance → Setup/Buffers → Buffers → Goto → Current local data → Additional functions → Storage → Shared memory detail.

You can change the pools and the shared memory segments with parameter ipc/shm_psize_<two-digit shared-memory id> .

You can change both the size and the location of the shared memory segment. The shared memory regions with the keys 10, 20, and 40 are used as shared memory pools by the SAP System. The size of these pools is determined by the values of the system profile parameters ipc/shm_psize_10 , _20 , and _40 .

ipc/shm_psize_10 =12000000

This parameter sets the size of shared memory pool 10 to 12,000,000 bytes. The shared memory pools must be large enough to hold the shared memory regions that belong to them. If you change the size of a region that belongs a pool, you must also change the size of the pool. You must also change the size of a pool if you add a new shared memory region to it.

For all other keys, this parameter can be used to define the position of the shared memory region. In this case the shared memory parameters have the following format:

ipc/shm_psize_nn = value

where nn is the SAP shared memory key and value is the attribute of the shared memory region.

Shared memory parameters

The SAP System uses the default disposition (in pool or directly allocated) of the shared memory region.

Table: Assignment of pools to keys

Object key	Pool
11 - 19	10
21 - 29	20 (not used currently)
41 - 49	40

All other objects are not located in a pool, as specified by the default settings.

A shared memory parameter ipc/shm_psize_nn can have the following values:

The value 0

The shared memory region is removed from its standard pool (if any) and is allocated directly by the operating system.

ipc/shm_psize_19 =0 removes the 100%-resident table buffer from its default pool 10. If your host operating system does not limit the number of shared memory allocations, you can remove shared memory regions from pools. Removing a region from a pool simplifies the maintenance of the system profile because you no longer need to adjust the size of a pool when you adjust the size of a region. If a region does belong to a pool, you must change the pool size in accordance with changes that you make to the shared memory regions in the pool.

A negative value

The shared memory region is assigned to the shared memory pool whose shared memory key is the same as the value.

ipc/shm_psize_33 =-10 adds the partial table buffer to shared memory pool 10.

Shared memory parameters other than those for keys 10, 20, and 40 should not have values greater than 0. Otherwise, the SAP System treats the shared memory region as a pool.

The default settings for the shared memory parameters will not be automatically found in the profile. They will only appear if they have been inserted manually, either to confirm or to change the default setting.