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

LSR - local shared resources
For LSR, data buffers are managed so that the buffers will not be overlaid. Before opening the
data set, the user builds a resource pool in private storage using the BLDVRP macro. The
LSR processing is as follows:
1. A GET request for record 1000 reads in the CI containing the record in one buffer of the
buffer pool.
2. The next GET request for record 5000, which is in a separate CI, will read in the CI in
another, separate buffer in the same buffer pool.
3. A third GET request for record 1001 can be satisfied by using the CI that was read in for
the request for record 1000.
GSR - global shared resources
GSR is the same concept as LSR. The only difference is, with GSR the buffer pool and VSAM
control blocks are built in common storage and can be accessed by any address space in the
system.
For more information about VSAM buffering techniques refer to 4.44, “VSAM: Buffering
modes” on page 177.
MACRF=(NSR/LSR/GSR)
The Access Method Control block (ACB) describes an open VSAM data set. A subparameter
for the ACB macro is MACRF, in which you can specify the buffering technique to be used by
VSAM. For LSR and GSR, you need to run the BLDVRP macro before opening the data set to
create the resource pool.
For information about VSAM macros, see z/OS DFSMS: Macro Instructions for Data Sets,
SC26-7408.
Chapter 7. DFSMS Transactional VSAM Services 381