Diagnosing Message Format Service problems

The number of physical terminals traced and the number of lines traced can affect completeness of trace records and sequence of trace entries.

  • Completeness of the trace record, (that is, whether or not all module activity related to a particular I/O action is traced), is affected if only one physical terminal (PTERM) is traced. The device-dependent module occasionally can change the current PTERM pointer before returning to the analyzer. Because the trace switch is kept in the CTB and is checked upon entry of a particular code, some module trace entries might be missing if the current CTB is not always maintained.
  • Sequence of entries can be broken if more than one line is traced at a time. In this case, entries for a particular line have to be related by CLB.
Trace records with the following identifiers are useful in diagnosing MFS problems.
DD6M
EDIT SEGMENT INTO TP BUFFER
CIB
MOD/DOF name
MFS SEG
SEGMENT created by MFS from output message and MOD/DOF
D01/DDM1
PREPARE TO WRITE TO TERMINAL
CIB
Offset X'00' contains 8-byte MOD name.

Offset X'0C' contains 8-byte DOF name.

A05
PRIOR TO ISSUING VTAM® I/O REQUEST (NORMALLY A WRITE)
O TP BUF
Contains the data to be written to the terminal and the RPL for VTAM devices. Refer to the previous A05 record.
A01
TERMINAL INPUT READY FOR IMS PROCESSING
I TP BUF
Contains input device segment 6 to 36 bytes from the beginning of the buffer. The data is preceded by a 2-byte length and 2 bytes of zeros.
FMT2
ENTRY TO MFS INPUT PROCESSING
CIB
Offset X'00' contains MID name.

Offset X'22' indicates if PFK or PA key is used.

X'80'
PA key
X'40'
PFK key
X'21'
PA or PFK number
FMT1
MESSAGE TO BE EDITED BY BASIC EDIT, NOT MFS
FMT3
MFS HAS COMPLETED A MESSAGE SEGMENT
MFS SEG
Shows input segment created by MFS.
MFS I WK
Shows complete input message (all segments) and internal segment control information used by DFSCFEI0.
MFS P WK
This trace record is displayed only when the content of a protected field that is returned from a 3270 or SLU2 device is altered.

Offset 4 contains the address of the altered field in the input buffer.

Offset 8 contains MOD name.

Offset x'10' contains DOF name.

Offset x'2C' points to the protected field entry (PFVENTRY).
PFVENTRY

Offset 0 points to the next entry.

Offset 4 is the length of the entry, which consists of an 8-byte header length and data length.

Offset 6 is the address of the device field buffer of the protected field.

Offset 8 is the original content of protected field.

ICLR
A message satisfied MSGDEL=NONIOBCB for its destination PTERM and was deleted. The relevant control blocks are traced:
  • Destination CTT
  • Telecommunication program communication block (TP PCB)
  • Destination CLB
  • Destination CTB

This trace record is produced when any trace level is active for the destination PTERM.

Note: To examine the segments placed in the message queue, see X'01' and X'03' log records. X'01' log records contain input message segments. X'03' log records contain output message segments.