Why we cant use the flat files(sequential file) in CICS

raghavmcs · Active User Joined: 14 Jul 2005 Posts: 105

I have not done any CICS programing just was curious why we cnt use the flat files(sequential file) in CICS programing,thanks

dick scherrer · Posted: Tue Jun 10, 2008 8:14 pm

Hello raghavmcs and welcome to the forums,

Typically because cics is a multi-user environment and qsam files are for a single user. QSAM files should be associated with batch processes, not online/cics processes.

bhushan.shete · New User Joined: 14 Nov 2006 Posts: 17

Hi Dick,

I agree with your answer but i have learnt that QSAM files are used by CICS
in case of extrapartition TDQ's.CICS uses PS datasets in the form of Extrapartition Transient Data Queue(TDQ).

also, QSAM file can be used by multi-user with disp=shr.

please correct me if i am wrong.

Aaru · Posted: Tue Nov 11, 2008 3:06 pm

Hi,

Robert Sample · Posted: Tue Nov 11, 2008 5:46 pm

A TDQ can be a sequential file. It's not common but it does work.

dbzTHEdinosauer · Posted: Tue Nov 11, 2008 6:16 pm

keep in mind that CICS is a online system.

do something, get out.

qsam implies continually doing something, that's BATCH.

Aaru · Posted: Tue Nov 11, 2008 6:16 pm

Robert,

Does that mean that files other than VSAM files can also be used in an online application? Please throw some light on this.

I don't have much online experience and the ONLY online project that i had worked on used only VSAM files.

Robert Sample · Posted: Tue Nov 11, 2008 6:41 pm

Aaru: Yes, sequential files can be used (in some cases). Transient Data Queue names can point to DD names that are included in the CICS startup JCL; the selected file is either an input-only or output-only file. You would use either READQ TD or WRITEQ TD to access the data in the file. It would not be a good idea to attempt to access this file from outside the CICS region while the region is active -- one of the reasons I said the usefulness is limited. Just to give you an idea, the values specified in the online resource definition are:

Aaru · Posted: Tue Nov 11, 2008 6:51 pm

Thanks a ton Robert for the information.

Ok I agree that sequential files can be used in few cases, but the input and output files can only be VSAM rite? Am I correct?

Robert Sample · Posted: Tue Nov 11, 2008 7:12 pm

Again, input and output files typically are VSAM but extrapartition TD queues (sequential files) can be input or output as well. You wouldn't want to drive your system with them, but you can use them for input or output if warranted.

Aaru · Posted: Tue Nov 11, 2008 9:35 pm

Thanks Robert. This is exactly what I wanted.

enrico-sorichetti · Posted: Tue Nov 11, 2008 9:45 pm

very awkward to manage with full data integrity,
IIRC extra partition transient data queues are not recoverable ,
in case of improper shutdowns data loss is almost certain

the same result can be obtained with proper output data integrity by using user journals

but check the manuals about the format of the cics journals

Robert Sample · Posted: Tue Nov 11, 2008 9:52 pm

enrico, I believe you're right that they're not recoverable -- not to mention you cannot read and write to them (only read from one or write to one -- one-way operations only). But they can serve some purposes.

enrico-sorichetti · Posted: Tue Nov 11, 2008 10:05 pm

continuation of previous posts ( clarification )

fortunately cics uptime is not an issue any longer,
but in case of emergency restarts extrapartition transient data queues
with mission critical data have always been a pain
for input there is no reposition, so operation support must clean up the dataset fed as input
or the program[s] using it must be told what to skip,
unless a plt program takes care of the positioning

for output data, apart from data loss, before a cics restart, the old data must be saved
and for later batch processing all the fragments must be consolidated and validated before use

I found that more than often the issues with extrapartion TD queue slowed down restarts in an unacceptable ways

many customer were relieved when user journals were introduced for output

babuprasad · New User Joined: 01 Jul 2008 Posts: 7 Location: bangalore

Any idea wat is the RDBACK used in the TYPE for???

enrico-sorichetti · Posted: Thu Nov 13, 2008 2:05 pm

a simple googling with "CICS RDBACK" will provide a link to the manual
with the info You ask for