When you migrate a VSAM file, you must add it to the CICS® VT DST so that CICS transactions can access the data in DB2®. To activate a change to the table, CICS VT must be stopped and restarted in the CICS region. Use the VTMI transaction for this purpose.
Specify one of the following parameters for the VTMI transaction:
If the MSTATUS of the new file is ACT, all calls to this file from CICS programs now access the data in DB2. If the MSTATUS is INACT, calls continue to be processed in VSAM. If you run the VTMI transaction with the STOP keyword, all VSAM calls for all files are processed by CICS.
The DST is explained in full in Adding a new data set to the CICS VT data set table.