CICS VT uses the DB2 call attachment facility (CAF) to connect to DB2.
For application programs that access VSAM data sets that have been migrated
using CICS VT and issue native SQL calls using the DB2 CAF attachment, there
are two scenarios to consider:
- Scenario 1: If the application program issues an SQL call before accessing
a CICS VT migrated data set, CICS VT subtasking is not required. CICS VT will
use the DB2 thread created by the application program CONNECT and OPEN to
process SQL calls to access the migrated VSAM data sets.
- Scenario 2: If the application program issues an SQL call after accessing
a migrated data set, the application program DB2 CONNECT request receives
a return code of 200 and a reason code of X'00C10201' if subtasking is not
enabled. If your application program tests this return code, it might signal
an error and abend the program. A DB2 return code of 0000 is returned if subtasking
is enabled.
Sub-tasking should be used in the second scenario to avoid having to change your application programs.