#1: Perfomance impact due to unused DD names Author: manu, Posted: Sun Oct 02, 2016 2:14 pm — One of the programs has about 300 output DD names.The number of output files getting created is based on the parm values passed.Say for a daily(controlled by parm) run only 100 files will be created.The program open and writes only the 100 files for the daily run.The other 200 files are not opened by the program for daily run.All the files are getting created in TAPE.Is there any perfomance impact due to having large number of Select statements in the program and DD names in the JCL.Some of them are not used for a run type which is controlled by parm.Please let me know.Thanks.
#2: Author: William Collins, Posted: Sun Oct 02, 2016 4:52 pm — No. If a file is not OPENed it is not going to directly affect performance of the program.
The program will be considerably larger than need be, and there may be effects from that.
There is "disposition processing", the JCL is going to take longer to process, and longer at end-of-step for having those unused DD names. I don't think either of those would be big problems.
When you say TAPE, you don't mean real TAPE, as in reel tape, do you? Look at the message output from your step, and see if there are "WAIT" messages of any type.
Last edited by William Collins on Mon Oct 03, 2016 12:12 am; edited 1 time in total
#3: Author: manu, Posted: Sun Oct 02, 2016 7:11 pm — Ok,Thanks for the information
