A thread executing in DB2® on behalf of a CICS® transaction is identified by its correlation ID set by the CICS DB2 Attachment Facility. DB2 allows up to 12 bytes to be used for the correlation ID. In releases of CICS before CICS Transaction Server for OS/390®, Version 1 Release 2, only 8 bytes were used.
The format 12 byte correlation ID is made up as as eeeettttnnnn where eeee is either COMD, POOL or ENTR indicating whether it is a command, pool or DB2ENTRY thread; tttt is the transid, and nnnn is a unique number.