MSS3 and MSS4 records
The MSS3 and MSS4 records capture link control blocks when links are started and stopped. MSS3 captures information when links are stopped. MSS4 captures information when the links are started.
MSC always logs the MSS3 and MSS4 records for diagnostics, even when a link trace is not active.
MSS3
The MSS3 record is a snapshot of the MSC link incore trace buffer for CTC, VTAM®, and TCP/IP links taken each time a link stops, either normally or due to an error.
The MSC link incore trace buffer, which is a wrap-around type buffer, contains data from selected fields in the link and I/O control blocks. MSC writes the data to the buffer each time a link is dispatched to do work and each time the link exits after completing the work. When the buffer is full, MSC wraps around and overwrites the oldest data in the buffer. Module DFSCMS80 contains the DSECTS of the selected fields that are written to the MSC link incore trace buffer.
The MSS3 record captures data from the following control blocks:
- LLB (logical link block)
- LTBs (link terminal blocks), input and output
- CRB (communication restart block)
- LXB (link extension block)
- I/O control blocks:
- For CTC-type links: IOSB, IOB, and IEDB
- For TCP/IP type links: SCIWORK
- For VTAM type-links: input and output RPLs (request parameter lists)
- R0 trace word
MSS4
The MSS4 record is a snapshot of link control blocks taken each time a link is started. The MSS4 record captures the following control blocks:
- LLB
- MSCWA
- LTBs, input and output
- I/O buffers, input and output
- LXB
- CRB
- I/O control blocks:
- For CTC-type links: IOSB
- For TCP/IP type links: SCIWORK
- For VTAM type-links: RPLs, input and output
- LNB (link name block for the MSNAME)
- CTT (communication terminal table block)