Trace Entries

Trace table entries can be 32 or 64 bytes. An entry's length and format are defined in its first two bytes:
  • the low-order half of the first byte: 7x, where x is the number of register fields minus one
  • the high-order bit of its second byte: y0, where y is 1 for 64-byte format and 0 for 32-byte format.
Thus the first two bytes of trace entries are:
  • 7400 - 32-byte entries in the format further described below
  • 7580 - 64-byte entries (this format is shown in Appendix C)

In addition to these first two bytes, trace table entries contain:

  • A time-of-day clock value that indicates when the entry was made
  • A constant field (0000)
  • A code that defines the event being traced
  • A maximum of 40 bytes of information about the specific event traced.

Figure 1 shows the format of a 32–byte trace entry as it would appear in a dump.

Figure 1. Format of a 32–byte Trace Entry
Format of a 32–byte Trace Entry

Each trace entry contains information on a specific system event. Consider the sample trace entry shown in Figure 2:

Figure 2. Sample Trace Entry in a CP Abend Dump
Sample Trace Entry in a CP Abend Dump

In this 32–byte trace entry at address X'00F83F80', the number over the blocks of storage refer to the following items:

  1. The time-of-day (TOD), bits 16 through 63, was set to X'877667F53000' when this trace entry was created (at X'02' in the trace entry).
  2. The trace event code was X'2C00', a RETURN WITH SAVE AREA (at X'0A' in the trace entry).
  3. The value returned in register 15 was X'0000000C' (at X'0C' in the trace entry).
  4. The condition code was 0, and the returning module identifier was ‘IID’ (at X'10' in the trace entry).
  5. The returned SAVBK address in register 13 was X'00FC0298' (at X'14' in the trace entry).
  6. The real address of the calling module from register 14 was X'00814488' (at X'18' in the trace entry).
  7. The real exit address of the called module from register 14 was X'8007BD3A' (at X'1C' in the trace entry).

In this example, CP stored the contents of the general purpose registers at X'FC0298' with a return code of 12.

For a complete listing of trace table codes and their field values, see Trace Table Codes.