On Oct 18 Tom Schmidt wrote: >You might have overlooked an interesting gem of a feature of z/OS JCL: >FREE=CLOSE.
>If you need to provide several alternative tables, you might be able to > do so >strictly in the enveloping JCL by doing something like this: >//SYSLIB DD DISP=SHR,FREE=CLOSE,DSN=USERS.INPUT(TABLEX) >//SYSLIB DD DISP=SHR,FREE=CLOSE,DSN=USERS.INPUT(TABLEY) >//SYSLIB DD DISP=SHR,FREE=CLOSE,DSN=USERT.MUMBLE(TABLEZ) >Note that the DDNAME is replicated three (3) times above, for example. >For the cost of a full OPEN/GET/CLOSE you get to read the record from > the >first member and be positioned to the second member on your next >OPEN/GET/CLOSE. Not high performance but pretty high function and very >easy to maintain (just change the JCL). > >z/OS does not limit DDNAMES to a single appearance in a step (although > you'd >be surprised how many think otherwise). By crafty use of multiple DDs > with >identical names that resolve to different datasets (even to completely >different data set names). Since any DD can use traditional data sets > or >PATH= it is also quite general. >Nearly every high level language supports file opens and closes so > nearly every >high level language can perform this "trick". >All you need to do is stop looping through the open/close once the open > fails. >(You ought to provide for error recovery if the open fails anyway so > that might >not be asking too much.) >/snip When I read this I thought it was pretty neat. Never had occurred to me that this was possible ... It is still neat to know. However, as a practical matter I could not think of an instance where it would be preferable to simply concatenating the data sets: //SYSLIB DD DISP=SHR,DSN=USERS.INPUT(TABLEX) // DD DISP=SHR,DSN=USERS.INPUT(TABLEY) // DD DISP=SHR,DSN=USERT.MUMBLE(TABLEZ) Only need one open and close. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
