Use ISAM access method in COBOL

Chetan Kumar · New User Joined: 03 Dec 2012 Posts: 46 Location: India

Hi All,

Is the usage of ISAM and KSDS in the cobol program is same?
Can we use ISAM access method in COBOL? If so, are there any changes to be made to the JCL to use the file or is it similar to KSDS file.

Bascially I want to know the difference between ISAM and KSDS (VSAM) from the programmers perspective.

Robert Sample · Posted: Tue Oct 13, 2015 10:51 pm

Are you talking about ISAM the generic indexed sequential access method, or are you talking about ISAM the IBM implementation? IBM stopped supporting ISAM many years ago as it was replaced by VSAM KSDS. VSAM KSDS is an indexed sequential access method. If your site is still using ISAM as implemented by IBM (and very few, if any, will be) -- you will need to discuss your questions and needs with your site support group as I'm sure there would have been numerous modifications to allow unsupported software to work on a current machine. If you just want to know about VSAM KSDS as an indexed sequential access method, there's a Redbook (http://www.redbooks.ibm.com) called VSAM Demystified that is quite good at explaining VSAM.

Chetan Kumar · New User Joined: 03 Dec 2012 Posts: 46 Location: India

It's about generic indexed sequential access method.

Bill Woodger · Posted: Tue Oct 13, 2015 11:12 pm

And what specifically do you mean by that?

Chetan Kumar · New User Joined: 03 Dec 2012 Posts: 46 Location: India

I want to know how the ISAM access method works inside Cobol Program. It is similar to KSDS or does there are changes in coding for accessing and to perform other operations.

Bill Woodger · Posted: Thu Oct 15, 2015 1:13 pm

If you look at an Enterprise COBOL Language Reference, do you see any specific treatment of VSAM-as-ISAM data?

Didn't the vendor let your client know, before the product was licensed? (If not, I've got a large bridge I'd like to sell to the client).

Have you just plain tried it? Attempted to locate documentation of the product? Done any search-engineing?

Chetan Kumar · New User Joined: 03 Dec 2012 Posts: 46 Location: India

Basically I'm not getting required info. I searched for ISAM and it's use.. but I didn't get proper results for us of ISAM access methond in COBOL program.

Many docs say it's very similar to VSAM. Bascially VSAM is enhanced form of ISAM. But coding usage, I'm not getting clear picture.

enrico-sorichetti · Posted: Fri Oct 16, 2015 12:35 pm

if You look at it from the IBM point of view
ISAM is an old access method/dataset organisation NO LONGER supported/provided/implemented

so Your question is a moot point

if on the other side You heard the word from some software provider ask them.

if You are curious about old ISAM just search bitsavers

Bill Woodger · Posted: Fri Oct 16, 2015 12:57 pm

Read Robert's original post. In your case, you are almost certainly talking about something other than KSDS-is-improved-ISAM. I've never used ISAM-ISAM, and I started a long time ago.

Just code it as a KSDS in your program, run your program.

PeterHolland · Posted: Fri Oct 16, 2015 2:06 pm

Look here :

www-01.ibm.com/support/knowledgecenter/SS6SG3_4.1.0/com.ibm.entcobol.doc_4.1/MG/igymch1013.htm

Chetan Kumar · New User Joined: 03 Dec 2012 Posts: 46 Location: India

Still some applications use OS/VS COBOL and ISAM files as the access method. So basically I want to know how to use ISAM files in OS/VS COBOL programs which runs on LINUX as the platform.

I appreciate if you can provide any docs,links etc

enrico-sorichetti · Posted: Fri Oct 16, 2015 7:35 pm

Bill Woodger · Posted: Fri Oct 16, 2015 7:55 pm

So after all this time you are really talking about ISAM-as-ISAM.

Wow. You'd better find your hardcopy OS/VS COBOL manual. There's lots of things different between OS/VS COBOL and Enterprise COBOL. Lots.

You get some idea from Peter's prescient link.

PeterHolland · Posted: Fri Oct 16, 2015 10:41 pm

steve-myers · Posted: Fri Oct 16, 2015 11:58 pm

Well, it's certainly possible to simulate ISAM within the file system. Effectively, that's what VSAM KSDS is doing in the mainframe. What the Cobol library is doing for the simulated ISAM is up to the writers of the library; you have to consult its documentation.

Pete Wilson · Posted: Sat Oct 17, 2015 1:18 am

Note: z/OS no longer supports indexed sequential (ISAM) data sets. Before migrating to z/OS V1R7, convert your indexed sequential data sets to key sequenced datasets.

I'm wondering if you're confusing ISAM with IAM (Innovation Access Method) which is kind of a progession of ISAM supported by Innovation Data Processing, and which is a very popular alternative performance access method for CICS datasets that would normally be VSAM format.

Rohit Umarjikar · Posted: Sat Oct 17, 2015 3:12 am

VSAM is the term IBM uses for one of its mainframe file systems (Virtual Sequential Access Method). It supports three formats: Indexed, Relative and Sequential access modes. Are you refering to converting an old IBM ISAM format to VSAM? If so, you would probably just unload the ISAM file to a sequential dataset and then use the IDCAMS services to define the new VSAM file and load the sequential file using Repro.

www-01.ibm.com/support/knowledgecenter/#!/SS6SG3_3.4.0/com.ibm.entcobol.doc_3.4/tpvsm02.htm

So answer to your questions, yes both are same infact VSAM is much better No changes required from programming stand poing, try and run with both the files instead of making gusses or forum answers.

Please Google it for more differences and the use.

Are you working on MF cobol or is it just another interview question?

Robert Sample · Posted: Sat Oct 17, 2015 11:26 pm

Pete Wilson · Posted: Sun Oct 18, 2015 12:30 am

and VRRDS