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

4.29 z/OS V1R9 QSAM - BSAM enhancements
DFSMS provides the following enhancements to
BSAM and QSAM:
Long-term page fixing for BSAM data buffers with the
FIXED=USER parameter
BSAM and QSAM support for the MULTACC
parameter
QSAM support for the MULTSDN parameter
Figure 4-39 QSAM and BSAM enhancements with z/OS V1R9
Long-term page fixing for BSAM data buffers
To improve performance, in z/OS V1.9 BSAM allows certain calling programs to specify that
all their BSAM data buffers have been page fixed. This specification frees BSAM from the
CPU-time intensive work of fixing and freeing the data buffers itself. The only restrictions are:
► The calling program must be APF authorized, or be in system key or supervisor state.
► The format of the data set must be either basic format, large format, PDS, or extended
format.
The DCBE macro option “FIXED=USER” must be coded to specify that the calling program
has done its own page fixing and indicates that the user has page fixed all BSAM data buffers.
Note: Compressed format data sets are not supported.
BSAM and QSAM support for MULTACC
In z/OS V1R9, the MULTACC parameter of the DCBE macro is expanded. This is done to
optimize performance for tape data sets with BSAM, and to support QSAM with optimized
performance for both tape and DASD data sets. The calculations that are used to optimize the
performance for BSAM with DASD data sets are also enhanced. When dealing with a tape
data set, OPEN supports MULTACC for BSAM and QSAM.
156 ABCs of z/OS System Programming Volume 3