If you are migrating to CICS® Transaction Server for z/OS®, Version 3 Release 1 from CICS/ESA 4.1 or CICS/ESA 3.3, you will need, for the first time, to define one or both of the following types of CICS log stream:
For advice on which log streams benefit from using coupling facility structures, and which DASD-only logging, see the CICS Transaction Server for z/OS Installation Guide.