Joined: 06 Jun 2008 Posts: 8218 Location: Dubuque, Iowa, USA
From the CICS Programming Guide:
3.2.7 Efficient sequential data set access
CICS provides a number of different sequential processing options. Temporary storage and intrapartition transient data queues (already discussed in "Temporary storage" in topic 220.127.116.11 and in "Intrapartition transient data" in topic 18.104.22.168) are the most efficient to use, but they must be created and processed entirely within CICS.
Extrapartition transient data is the CICS way of handling standard sequential (QSAM/BSAM) data sets. It is the least efficient of the three forms of sequential support listed, because CICS has to issue operating system waits to process the data sets, as it does when handling BDAM. Moreover, extrapartition transient data sets are not recoverable. VSAM ESDSs, on the other hand, are recoverable within limitations, and processing is more efficient. The recovery limitation is that records added to an ESDS during an uncompleted UOW cannot be removed physically during the backout process, because of VSAM restrictions. They can, however, be flagged as deleted by a user exit routine.