Allocating auxiliary trace data sets

If you are defining auxiliary trace data sets on disk, you can use the job shown in Figure 16 to allocate and catalog them before running CICS®.

Alternatively, you can run the CICS-supplied job DFHDEFDS to create the auxiliary trace data sets for an active CICS region or the CICS-supplied job DFHALTDS to create them for an alternate CICS region. For information about the jobs DFHDEFDS and DFHALTDS, see the CICS Transaction Server for z/OS® Installation Guide.

Figure 16. Sample job to define auxiliary trace data sets on disk
//DEFTRCDS JOB (accounting information),
//             MSGCLASS=A,MSGLEVEL=(1,1),
//             CLASS=A,NOTIFY=userid
//*********************************************************************
//*            Create auxiliary trace data sets
//*********************************************************************
//ALLOCDS  EXEC PGM=IEFBR14
//DFHAUXT  DD  DSN=CICSTS31.CICS.applid.DFHAUXT,UNIT=3380,VOL=SER=volid,
//         DISP=(NEW,CATLG),DCB=(BLKSIZE=4096,RECFM=F,LRECL=4096),   1 
//              SPACE=(CYL,(5,1))                                    2 
//DFHBUXT  DD  DSN=CICSTS31.CICS.applid.DFHBUXT,UNIT=3380,VOL=SER=volid,
//         DISP=(NEW,CATLG),DCB=(BLKSIZE=4096,RECFM=F,LRECL=4096),   1 
//              SPACE=(CYL,(5,1))                                    2 
//

Notes:

 1  The DCB subparameters shown in this sample job specify the required DCB attributes for the CICS auxiliary trace data sets. As an alternative to this job, you can specify (NEW,CATLG) on the DD statements in the CICS startup job stream, omit the DCB parameter, and let CICS open the data sets with the same default values.

 2  Change the space allocations in this sample job stream to suit your installation’s needs.

Space calculations

Trace entries are of variable length, but the physical record length (block size) of the data written to the auxiliary trace data sets is fixed at 4096 bytes. As a rough guide, each block contains an average of 40 entries, although the actual number of entries depends on the processing being performed.

Job control statements for CICS execution

If you allocate and catalog the auxiliary trace data sets on disk as shown in Figure 16, you can define them to CICS in the startup job stream with the following DD statements:

//DFHAUXT  DD  DSN=CICSTS31.CICS.applid.DFHAUXT,DCB=BUFNO=n,DISP=SHR
//DFHBUXT  DD  DSN=CICSTS31.CICS.applid.DFHBUXT,DCB=BUFNO=n,DISP=SHR

If you specify BUFNO greater than 1, you can reduce the I/O overhead involved in writing auxiliary trace records. A value between 4 and 10 can greatly reduce the I/O overhead when running with auxiliary trace on.

DISP=SHR allows the simultaneous processing of a data set by the DFHTU640 offline utility program after a switch to the other data set has taken place.

For auxiliary trace data sets on unlabeled tapes, use the following sample DD statements:

//DFHAUXT  DD  DSN=CICSTS31.CICS.applid.DFHAUXT,UNIT=3400,VOL=SER=volid,
//         DISP=(NEW,KEEP),LABEL=(,NL)
//DFHBUXT  DD  DSN=CICSTS31.CICS.applid.DFHBUXT,UNIT=3400,VOL=SER=volid,
//         DISP=(NEW,KEEP),LABEL=(,NL)

If you are using tape for the auxiliary data sets, assign tape units and mount the tapes before entering the command to start auxiliary trace. If you specify AUXTR=ON as a system initialization parameter, ensure the tape is mounted before starting CICS.

XRF considerations

The active and the alternate CICS regions must refer to different auxiliary trace data sets; that is, they must be unique data sets. This means that you can capture auxiliary trace data for the active CICS region, while the alternate CICS region is running but before takeover occurs.

For the active CICS region, you use CETR or CEMT to control auxiliary trace data sets. For the alternate CICS region, you use CEBT. For information about using these transactions, see CICS Supplied Transactions.

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