Getting a dump of CICS and other address spaces when CICS is at MAXTASK

When a CICS region goes MAXTASK, a bit in the CICS Common System Area (CSA) is turned on. In the CICS CSA at offset +x'49' is field CSAKCMI. In that field, the x'02' bit is called CSAMXTON.

This bit is normally off, '0', but when CICS goes MAXTASK, it gets turned on, '1'. You can set an MVS Storage Alter SLIP trap on the CSAMXTON bit to have MVS capture an SVC dump, and optionally dump any other address space. To do that, you need the address of the CSA in the running region. The easiest way to get that is through a CICS monitor product like OMEGAMON.

Once you have the CSA address, the SLIP trap would look like this

 SLIP SET,SA,J=jjjjjjjj,ASIDSA=SA,A=SVCD,RA=(xxxxxxxx),
   DATA=(xxxxxxxx(6),EQ,1),
   SDATA=(ALLNUC,CSA,PSA,SQA,LSQA,TRT,SUM,RGN,LPA,GRSQ),END

Where
jjjjjjjj = the CICS jobname
xxxxxxxx = "start of CSA" plus x'49'.

Note that the address of the CSA may change if the CICS region is recycled, so the SLIP trap would need to be modified anytime that happens. You can update the SLIP trap to dump other address spaces as needed by adding the JL= parameter. At the time this was written the offsets in the CSA were valid for all supported releases of CICS TS, V4.1 through V5.3. If you working with newer releases, make sure the offsets have not changed.