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This Idea is being rejected based on comments from Oct 26 and Nov 10th.
Hi Denis, one correction to the previous update, you cannot change DDNAME, but you can change which file you are accessing dynamically at run time,which is basically what having different DDNAMEs would provide. Thanks.
Hi Denis,
You can use dynamic allocation to change DDNAMEs at runtime. Please have a look at the COBOL Programming Guide under 'Allocating files' and the 'environment-variable' sections:
https://www.ibm.com/docs/en/cobol-zos/6.4?topic=files-allocating
Hi,
I would like to control the ddnames when running the program, in order to develop utilities that I could integrate into IBM Dependency Based Build scripts.
As the same utility program could be executed several times in a IBM DBB Job, or use files produced in previous IBM DBB steps, IBM DBB forces the ddnames to be modified at runtime (otherwise errors are triggered in BPXWDYN if the ddname is already used).
Hi Denis, can you please clarify if you need the ability to process DDNAMES at COBOL runtime of your own application or at COBOL Compile time?
Hi,
After research, I understood that indeed the ddname files allocation list were managed programmatically, and that this supposed to use some form of parameters passing which is perhaps not compatible with high level languages like COBOL, which expect a list of parameters in the form of a sequence of addresses pointed to by register R1.
The information should be passed through the PARM= option on the EXEC PGM line, in 2nd position, and in the format of a characters string preceded by 2 binary bytes containing the length of the string...
If it was a 1st position, we could retrieve the information by the PROCEDURE USING of a COBOL program... but in 2nd position I don't know how to do it in COBOL...
Hi Dennis,
The order of the ddnames in an alternate ddname list is determined and supported by the application itself (eg. the COBOL compiler) to which the alternate ddname list is passed. From the perspective of implementing something like this in a COBOL program, you'd need the ability to open a file with a ddname other than what's in the ASSIGN clause for the file.
Currently there is the ability to do ASSIGNment via an environment variable (see https://www.ibm.com/docs/en/cobol-zos/6.4?topic=section-assign-clause ), one possible solution would be to extend this with a DDNAME() option (in addition to the current DSN() and PATH() options).
Bernie