Command Trace Area—eyecatcher “CMDTRACE”. The command trace records the last 10 calls to tableBASE in this region. This area is only present if the TRACE Status Switch (Switch 5) is set to Y. Each entry consists of a before and after image of the command area and TBPARM.
The command trace area has a header which contains an address (@+14) which is used for the next trace entry; so the last entry is the one just before this pointer. The trace table wraps, so there may be a residual trace entry in the “next” entry. If an abend occurs while processing a command, the before entry will be there, but not the after.
0000 CMTHEYEC DC CL8'CMDTRACE' eyecatcher
0008 CMTHSIZE DS AL4 Total size of CMDTRACE area
000C CMTHENTL DS AL4 Size of each entry (COMMAND + TBPARM)
0010 CMTHSTRT DS AL4 addr of first trace table entry
0014 CMTHNEXT DS AL4 addr of next trace table entry to use
0018 CMTHEND DS AL4 addr of end of trace table entries
001C DS AL4 Reserved for future use
0020 start of entries, each of which contains:
+00 COMMAND AREA (length 72 bytes)
+48 TBPARM (length 64 bytes)