CA Datacom VSAM Transparency (DBVT) Version 14.0 provides enhancement via PTF SO00347.
As noted in informational SI04046 :
We have enhanced DVREQPR to be THREADSAFE. DVREQPR is called for any CICS File Control commands from any application when the CA Datacom VSAM Transparency (DBVT) is active, that is, when Global User Exit (GLUE) DVFCREQ is enabled.
This enhancement allows THREADSAFE applications to avoid TCB switching. If the application code is THREADSAFE and runs on an Open TCB such as L8 or L9, then GLUE DVFCREQ and program DVREQPR would also run on L8 or L9 as well. If, however, the application code runs on a Quasi Re-entrant (QR) TCB, then DVREQPR would continue running on the QR TCB.
This feature eliminates unnecessary TCB switching for THREADSAFE applications making file control calls of any kind while DBVT is active. The enhancement is delivered by PTF SO00347.