Thursday, December 07, 2006

Review topic: JCL, MVS

hiperspace -- comparable to a dataspace but resides in extended storage and helps jobs run more efficiently

ICF -- Integrated Cataloge Facility
VSAM files must be catalogued

JES3 ADDRSPC VIRT is default REAL means storage is non-pageable

DCB you can use OPTCD to read and write data in ASCII

examples of pre-printed forms

or for laser printer

The OUTPUT statement is used to specify parameter sets for multiple SYSOUT DD's within a particular step. The DEFAULT=YES on an output statement makes the parameters apply to all SYSOUT DDs that don't specify an alternate statement. The DEST subparameter is often used to direct specific forms to other remote printers. In practice, when doing laser printing, many shops require that the programmer insert various special characters in the print line to further control printing, especially in automated stacks with client breaks indicated by various colored papers (agent commission statements, for example). Printer vendors sometimes require content control that goes beyond what is commonly accomplished by JCL output control parameters and subparameters.

Remember that in cataloguing or referencing a tape dataset, the VOL parameter is very useful. A number after the second comma may reference which reel of a multiple volume set, and the number after the third comma can specify the max reels to create. A default of 5 is assumed. In one small consulting company in 1989 (in a 4381 environment, the "small" mainframe of the time), we kept summary data on multi-file reels, and had to be very skilled in reading them back correctly with various parameters; we were in an environment where we paid for disk space and computer time and had an economic incentive to resue summary data. (We also had to manipulate the Medpar detail on various volumes a lot.) Times have changed tremendously since then!

It is often desirable and more professional to allocate temporary datasets within virtual storage. UNIT=VIO will accomplish this. Surprisingly, many shops do not bother to do this. Shops generally encourage the use of temp sets, however, and will monitor programmers' use of unnecessary catalogued datasets.

JES2 and JES3 handle scheduling jobs on specific processors differently. In JES2 you use the /*JOBPARM statement with the system affinity (SYSAFF) parameter. In JES3 you use the //*MAIN statement (two slashes) with the SYSTEM parameter. A global processor is in charge of a whole network, and controls local processors.

Back in the late 1970s at Bradford we used CHKPT a lot on tape jobs, because we had sequential jobs that processed millions of records of MMIS claims data tapes. The EOV parameter takes a checkpoint at the end of writing each volume. This was very useful in being able to finish production processing in time, especially with programmers on call on their own salaried time.


erodeboy said...

can u send me the questions asked during online exam to my mail id Thanks in advance

Bill Boushka said...

No, I can't supply exam questions. They are confidential and that would be unethical and illegal. What I do is make general review notes. I haven't even taken the test. Some of the notes on this blog, if you look at them, are general summaries of things that happened in my career (30 years). Besides exams, I try to forewarn others from making the same mistakes that I did, or almost did. Bill

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