ABCs of z/OS System Programming Volume 3 - IBM Redbooks

4.43 VSAM resource pool
VSAM resource pool is formed by:
I/O control blocks
Buffer pool (set of equal-sized buffers)
VSAM resource pool can be shared by VSAM
clusters, improving the effectiveness of these
buffers
Four types of VSAM buffering techniques:
Non-shared resource (NSR)
Local shared resource (LSR)
Global shared resource (GSR)
Record-level sharing (RLS)
Figure 4-53 VSAM resource pool
VSAM resource pool
Buffering is one of the key aspects as far as I/O performance is concerned. A VSAM buffer is
a virtual storage area where the CI is transferred during an I/O operation. In VSAM KSDS
there are two types of buffers: buffers for data CIs and buffers for index CIs. A buffer pool is a
set of buffers with the same size. A resource pool is a buffer pool with several control blocks
describing the pool and describing the clusters with CIs in the resource pool.
The objective of a buffer pool is to avoid I/O operations in random accesses (due to re-visiting
data) and to make these I/O operations more efficient in sequential processing, thereby
improving performance.
For more efficient use of virtual storage, buffer pools can be shared among clusters using
locally or globally shared buffer pools. There are four types of resource pool management,
called modes, defined according to the technique used to manage them:
► Not shared resources (NSR)
► Local shared resources (LSR)
► Global shared resources (GSR)
► Record-level shared resources (RLS)
These modes can be declared in the ACB macro of the VSAM data set (MACRF keyword)
and are described in the following section.
176 ABCs of z/OS System Programming Volume 3