CICS® trace entries can be directed to auxiliary trace data sets, which are CICS-owned BSAM data sets. If you want to use auxiliary trace, you must create the data sets before you start CICS;
you cannot define them while CICS is
running.
About this task
Auxiliary trace is held in one or two sequential data sets, on either disk or tape. The DD names
of the auxiliary trace data sets are defined by CICS as
DFHAUXT and DFHBUXT. If you define a single data set only, its DD name must be DFHAUXT.
If you are using both data sets, you can use the auxiliary switch (AUXTRSW
system initialization parameter) to specify that auxiliary trace data cannot be overwritten by
subsequent trace data.
Trace entries are of variable length,
but the physical record length (block size) of the data that is written
to the auxiliary trace data sets is fixed at 4096 bytes. As a rough
guide, each block contains an average of 40 trace entries, although
the actual number of trace entries depends on the processing that
is being performed.
Decide whether to define one or two sequential data sets
for auxiliary trace.
If you want to specify automatic switching
for your auxiliary trace data sets, you must define two data sets.
If you specify automatic switching for auxiliary trace, but define
only one data set, auxiliary trace is stopped and a system dump is
generated.
Decide on the location of the auxiliary trace data sets.
If you use tape for recording auxiliary trace output, use unlabeled tape. Using
standard-labeled tape, whether on a single tape drive or on two tape drives, stops you processing
the contents of any of the volumes with the CICS trace utility program, DFHTUnnn
until after the CICS step has been completed. If you have to
use standard-labeled tape, make sure all the output produced in the CICS run fits on the one or two volumes mounted.
You cannot
catalog data sets that are on unlabeled tapes.
If you are defining auxiliary trace data sets on disk,
allocate and catalog the auxiliary trace data sets before you start CICS. Use one of the following
methods:
Use the supplied job DFHDEFDS to create the auxiliary trace
data sets. For more information, see Creating the CICS data sets.
If you are using tape for the auxiliary data sets, and
you want auxiliary trace to be active from CICS startup, assign tape units and mount the
tapes before you start CICS.
If you plan to start auxiliary trace by entering a command when CICS is running, ensure the tapes
are mounted before you enter the command.
Define the auxiliary trace data sets to CICS in
the startup job stream.
For auxiliary trace data sets on disk
For auxiliary trace data sets on disk, use the following DD statements as examples. In the
example DD statements, the data set names have prefixes that reflect the release of CICS TS, and the
release level is assumed to be CICS TS6.2.
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 CICS trace
utility program, DFHTUnnn after a switch to the other data set has taken place.
DFHTUnnn is an offline utility program that has a unique release identifier in
its name. For example, it is DFHTU750 for
CICS TS6.2.
For auxiliary trace data sets on unlabeled tapes
For auxiliary trace data sets on unlabeled tapes, use the following sample DD statements. In the
sample, the data set names have prefixes that reflect the release of CICS TS, and the release level
is assumed to be CICS TS6.2.
If you are defining auxiliary trace data sets on disk, you can use this sample job to allocate
and catalog them before you run CICS.
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.
Change the space allocations in this sample job stream to suit your installation's needs.
In the sample job stream, the high level qualifier
(CICSTSnn.CICS) assumes the release level of CICS TS6.2. You must adapt it for your own
CICS release.