CICS® records transaction dumps on a sequential data set, or a pair of sequential data sets, on disk or tape. The data sets must be defined in the CICS run with the DD names DFHDMPA and DFHDMPB, but if you define a single data set only, its DD name must be DFHDMPA. In this section, a reference to "the CICS dump data set" means either DFHDMPA or DFHDMPB. Note that CICS always attempts to open at least one transaction dump data set during initialization. If you do not include a DD statement for at least one transaction dump data set in your CICS job, initialization continues after the following message is sent to the console:
DFHDU0306 applid Unable to open Transaction Dump Data set
dataset-text-descr
With two data sets, you can print transaction dumps from one data set while CICS is running. To do this, first use CEMT SET DUMP SWITCH to switch the data sets. CICS closes the current data set after any transaction dump being recorded has been completed, and opens the other data set. You can print the completed data set with the DFHDU640 dump utility program. For information about the DFHDU640 dump utility program, see the CICS Operations and Utilities Guide.
In addition to switching dump data sets explicitly, the operator can use CEMT SET DUMP AUTO to cause automatic switching when the current data set becomes full. (Note that this permits one switch only.) When a transaction dump data set is full, CICS closes the data set and issues console messages as follows:
DFHDU0303I applid Transaction Dump Data set dataset closed.
DFHDU0304I applid Transaction Dump Data set dataset opened.
DFHDU0305I applid Transaction Dump Data set switched to ddname.
where "x" and "y" can have the value A or B. If you specified DISP=SHR for the dump data set, you can print the completed data set with the DFHDU640 utility program and then reissue the command: CEMT SET DUMP AUTO. This again switches data sets automatically (once only) when the current data set is full.
You can define the CICS dump data sets DFHDMPA and DFHDMPB as temporary data sets for each CICS run. More commonly, you allocate and catalog them in advance, reuse them repeatedly, and do not delete them when the CICS job has completed. You can then use the DFHDU640 utility program to print the dump output at any time during or after the CICS run. Note that it is not practical to try to use temporary data sets when running CICS with XRF.
You do not need DCB parameters for dump data sets (but see Copying disk dump data sets to tape for an exception). When CICS opens the dump data set, it issues an MVS™ DEVTYPE macro. This returns the track size for direct access devices, or 32760 for magnetic tape. The maximum block size used for a transaction dump is the lesser of the values returned from the DEVTYPE macro and 4096. As this usually results in a block size of 4096 (because devices generally have a track size greater than this), CICS writes multiple blocks per track. After writing each block, MVS returns the amount of space remaining on the current track. If the space remaining is 256 bytes or more, then the size of the next block written is the lesser of the values returned by MVS and 4096.
If the space remaining is less than 256 bytes, the next block is written to the next track.
There are four global user exits that you can use with the transaction dump data sets:
For programming information about the global user exits, see the CICS Customization Guide
You can code the DUMPDS system initialization parameter to specify which transaction dump data set is to be opened during CICS initialization. If you specify DUMPDS=AUTO, CICS opens, on a warm or emergency start, the data set that was not in use when CICS was last terminated. This lets you restart CICS after an abnormal termination without waiting to print the dump data set that was in use at termination. For more information about the DUMPDS parameter, see Specifying CICS system initialization parameters.
[[ Contents Previous Page | Next Page Index ]]