Specifying sequential buffering control statements
You can use six different sequential buffering control statements, SBPARM, SBIC, SBCO, SBSNAP, SBESNAP, and SNAPDEST, to specify and override definitions related to sequential buffering.
SB control statements allow you to:
- Specify which I/O operations should be buffered by the SB buffer handler
- Override the default number of buffer sets to increase buffering performance
- Experiment with SB specifications without changing exit routines or regenerating the PSB
- Use SB problem determination aids
SB control statements are in a data set with the ddname of //DFSCTL. You can provide a //DFSCTL DD statement in the JCL of the IMS batch or IMS dependent online region. The //DFSCTL DD statement must point to a sequential data set or a member of a partitioned data set. The record format of the //DFSCTL data set must be F, FB, or FBS.
Sequential buffering can be invoked by default for IMS utilities, such as online image copy, without requiring SB control statements, through the use of the SB Initialization exit routine.
Related reading:
- For the syntax and keywords associated with the SB control statements, see Sequential buffering control statements.
- For the description of the SB Initialization exit routine, see IMS Version 15.5 Exit Routines.