Processing data sets using a path can increase the number of buffers that need to be allocated, since buffers are needed for the alternate index, the base cluster, and any alternate indexes in the upgrade set.

The BUFSP, BUFND, BUFNI, and STRNO parameters apply only to the path's alternate index when the base cluster is opened for processing with its alternate index. The minimum number of buffers are allocated to the base cluster unless the cluster's BUFFERSPACE value (specified in the DEFINE command) or BSTRNO value (specified in the ACB macro) permits more buffers. VSAM assumes direct processing and extra buffers are allocated between data and index components accordingly.

Two data buffers and one index buffer are always allocated for each alternate index in the upgrade set. If the path's alternate index is a member of the upgrade set, the minimum buffer increase for each allocation is one for data buffers and one for index buffers. Buffers are allocated to the alternate index as though it were a key-sequenced data set. When a path is opened for output and the path alternate index is in the upgrade set, specify ACB MACRF=DSN and the path alternate index shares buffers with the upgrade alternate index.