This topic is intended to help you share resources among your VSAM data sets. VSAM has a set of macros that lets you share I/O buffers and I/O-related control blocks among many VSAM data sets. In VSAM, an I/O buffer is a virtual storage area from which the contents of a control interval are read and written. Sharing these resources optimizes their use, reducing the requirement for virtual storage and therefore reducing paging of virtual storage.

Sharing these resources is not the same as sharing a data set itself (that is, sharing among different tasks that independently open it). Data set sharing can be done with or without sharing I/O buffers and I/O-related control blocks. For information about data set sharing see Sharing VSAM Data Sets.

There are also macros that let you manage I/O buffers for shared resources.

Sharing resources does not improve sequential processing. VSAM does not automatically position itself at the beginning of a data set opened for sequential access, because placeholders belong to the resource pool, not to individual data sets. When you share resources for sequential access, positioning at the beginning of a data set has to be specified explicitly with the POINT macro or the direct GET macro with RPL OPTCD=NSP. You may not use a resource pool to load records into an empty data set.