Be safe, know the threadsafe file control performance differences starting in CICS Transaction Server 3.2
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If you are upgrading to CICS Transaction Server for z/OS (CICS TS) V3.2 or higher, and are seeing performance differences for transactions that heavily use file control, for example, some of your transactions are using much more CPU. Note that in CICS Transaction Server V3.2 there are changes to enable file control thread safety that might result in performance differences for transactions that heavily use file control.
To tune your CICS region in order to improve the performance for transactions using file control,make the system initialization table (SIT) and resource definition changes as described in the attachment provided by IBM CICS Support:
Please note that the aforementioned document was originally written for CICS TS V3.2 but it is also applicable to higher releases of CICS like CICS TS V4.1 and V4.2.