OSAM subpool definition

OSAM subpools are defined using the IOBF and DBD statements. Specify the required subpools in the DFSVSAMP data set for batch environments, or in the DFSVSMxx member of the IMS PROCLIB data set for DB/DC environments. When using OSAM to access VSAM Linear data sets (LDS), the data is stored in the OSAM buffer pool. Supply enough OSAM buffer pool definitions (IOBF) to hold these data sets.

You can define multiple OSAM subpools as having the same buffer size (that is, the length parameters specified on the IOBF subpool definition statements are identical); then, you can direct given data sets to specific subpools. To take advantage of this flexibility, the subpool must have a user-defined ID (using the ID subparameter) and a DBD statement coded to identify the data set.

If you do not want to assign data sets to specific subpools, do not code the DBD subpool definition statement. If you define multiple OSAM subpools having the same buffer size and ID, IMS generates only one subpool for that buffer size. Within this subpool, the number of buffers is equal to the sum of the number of buffers specified for these subpools. The OSAM buffers and control blocks are above the 16 MB line. In a batch environment, the OSAM buffers and control blocks are located in the private address space. You must allocate a region size that is large enough to accommodate your OSAM buffer requirements.