BPCSIZE - Cache Size for Natural Buffer Pool

This Natural profile parameter specifies the size of the buffer pool cache (in KB) for a Natural local buffer pool.

Possible settings 0 If BPCSIZE=0 is set, no buffer pool cache is used.
100 - 2097148

(2 GB - 4 KB)

The buffer pool cache size in KB for cache in data space; that is, with C64=OFF.

The specified value is rounded to the next 4 KB boundary.

100 - 58720256

(56 GB)

The buffer pool cache size in KB for cache "above the bar"; that is, with C64=ON.

The specified value is rounded to the next 1 MB boundary.

Default setting 0 By default, no buffer pool cache is used.
Dynamic specification yes This parameter can only be specified dynamically.
Specification within session no


  1. This Natural profile parameter is applicable under z/OS and z/VSE only (not for Com-plete and not for IMS TM).
  2. It corresponds to the CSIZE subparameter of the BPI profile parameter or NTBPI macro.
  3. Internally, the BPCSIZE specification is converted into the equivalent BPI specification, for example: BPCSIZE=4000 is converted into BPI=(TYPE=NAT,SEQ=0,CSIZE=4000).
  4. If the value specified exceeds the possible maximum, the possible maximum value will be taken instead.
  5. The BPCSIZE parameter applies to the primary Natural buffer pool (TYPE=NAT, SEQ=0) only. In the case of a Natural global buffer pool, it is ignored. If there is a primary buffer pool with SEQ=0 in the Natural parameter module, only the cache size setting of this buffer pool is updated.
  6. In multi-user environments (for example, under CICS), the BPCSIZE parameter affects the very first Natural session only, which initializes the Natural local buffer pool.
  7. The type of storage to be used for the buffer pool cache is determined by profile parameter BPC64 or subparameter C64 of profile parameter BPI or macro NTBPI.
  8. For more information, see Buffer Pool Cache in the Operations documentation.