Sequential buffering service aids
When you receive a message or abend that indicates a problem with sequential buffering (SB), several diagnostic tools are available. Some of these tools are useful for diagnosing other IMS database-related problems.
Useful tools for diagnosing IMS data-related problems
- DL/I trace table entries
- Dump formatting of IMS control blocks
- SNAPs of IMS control blocks during pseudoabends
The //DFSSTAT statistics report is also a useful tool for evaluating a potential sequential buffering problem.
SB provides additional problem determination tools, which are described in this section:
- SBSNAP and SBESNAP options
- SB IMAGE CAPTURE option and the SB Test program (DFSSBHD0 utility)
- The SB COMPARE option
For most invocations of SB pseudoabend buffer handler functions, entries in the DL/I trace tables are provided. The SB trace table entries are:
- X'6F'
- Search/read by RBN
- X'6C'
- Refresh SB buffer after a write
- X'69'
- Invalidate SB buffers
- X'6A'
- Evaluate SB buffering
- X'6B'
- Describe why SB was or was not used for the application
In addition, the X'D1' DL/I trace table entry created by DFSNOTB0 contains some information about invalidation of SB buffers.