TRACE CT command

Use the z/OS® TRACE CT command to start, stop, or modify an IRLM diagnostic trace.

IRLM does not support all the options available on the TRACE CT command.

Subsections:

Syntax

Read syntax diagramSkip visual syntax diagramTRACECT,WTRSTART= parmlibmem,WRAP,NOWRAPWTRSTOP= jobnameON,COMP= irlmnm,SUB=(DBMEXPINTSLMXCFXIT)1OFF
Notes:
  • 1 The same trace type can be specified only once.

Keywords

The following keywords can be specified for the TRACE CT command.
CT
Specifies the component trace (instead of the other trace options available on the z/OS TRACE command).
WTRSTART=parmlibmem
Identifies the name of the member that contains the source JCL that invokes the external writer and defines the data set to which external writer writes the trace buffers. The member can be a SYS1.PROCLIB cataloged procedure or a job. Many installations use a cataloged procedure in SYS1.PROCLIB.
After you enter a TRACE CT,WTRSTART command, turn the trace on and connect the writer using the WTR parameter in the reply for a TRACE CT command.
WRAP
Specifies that when the system reaches the end of the data set or group of data sets, it writes over the oldest data at the start of the data set or the start of the first data set in the group. The primary extents of the data set are used.
NOWRAP
Specifies that the system stops writing to the data set or data sets when they are full. The primary and secondary extents of the data sets are used.
WTRSTOP=jobname
Identifies the job name of a component trace external writer to be stopped. The data sets that the writer used are closed.
The job name is either:
  • A member name, if the source JCL is a procedure.
  • The name on a JOB statement within the source JCL.
ON
Turns on the trace.
COMP=irlmssnm
The IRLM subsystem name.
SUB=subname
Identifies the type of sublevel trace desired. This parameter can be any of the following values:
DBM
Trace interactions with the identified DBMS.
EXP
Trace any exception condition. EXP is automatically turned on when IRLM starts running and is permanently turned on.
INT
Trace member and group events outside of normal locking activity. INT is automatically turned on when IRLM starts running and is permanently turned on.
SLM
Trace interactions with the z/OS locking component.
XCF
Trace all interactions with z/OS Cross-System coupling services.
XIT
Trace just asynchronous interactions with the z/OS locking component. XIT is automatically turned on when IRLM starts running, but it can be turned off using the z/OS TRACE CT command.
OFF
Turns off the trace. If IRLM is connected to a component trace external writer, the system forces an implicit disconnect.

In the case of the EXP and INT sublevel traces, the OFF parameter stops the traces from writing to the external writer. However they continue to write to buffers. These traces are used by IMS for debugging purposes.

Sample external writer procedure

Here is a sample procedure for the IRLM external writer: 
//CTWTR    PROC
//         EXEC PGM=ITTTRCWR
//TRCOUT01 DD   DSNAME=SYS1.WTR1,DISP=OLD
//TRCOUT02 DD   DSNAME=SYS1.WTR2,DISP=OLD

Usage notes

The impact of setting TRACE CT ON is that each active subname type requires up to .7 MB of ECSA. Because IRLM initializes its own traces when it starts, the DISPLAY TRACE command shows that all traces are off. After you issue the TRACE ON command, the reports are accurate except for the two subname types, INT and EXT, which cannot be turned off.

This command can be entered only from the master console. The command requires an appropriate level of z/OS authority.

Because this command uses z/OS component trace services, make sure that the IRLM start and stop load module, DXRRL183, is in the z/OS link list.

Examples

Here are some examples of using the TRACE CT command.

Example 1 for TRACE CT command

Here is an example sequence of commands to start and stop an IRLM DBM trace. In this example, the trace data is written to an external writer data set identified in procedure CTWTR: 
TRACE CT,WTRSTART=CTWTR
TRACE CT,ON,COMP=IRLM,SUB=(DBM)
⋮
  (z/OS asks for a reply.)
⋮
R 15,WTR=CTWTR,END
TRACE CT,OFF,COMP=IRLM,SUB=(DBM)
⋮
  (Wait a while to make sure trace buffers are externalized.)
TRACE CT,WTRSTOP=CTWTR

Example 2 for TRACE CT command

Here is a sample procedure to start and stop traces in wrap-around mode. The traces captured in this procedure are saved in a limited number of buffers that are provided by IRLM. Each buffer is reused when the previous buffer is filled. 
TRACE CT,ON,COMP=IRLM
⋮
  (z/OS asks for a reply.)
⋮
R 15,END
TRACE CT,OFF,COMP=IRLM