Virtual Storage



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Virtual Storage

Postby boy_frame » Mon Aug 16, 2010 4:06 pm

What does insufficient virtual storage means?
If I have a 14 million of records what could be its appropriate TRACKS or CYLINDER definition in jcl's delete define of a VSAM file?
What could be a correct delete define having 14 million records,VSAM file,indexed or KSDS and a blksize of 149,and is FB?Help please I cannot accomodate those records to be transferred in its VSAM file.
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Re: Virtual Storage

 

Re: Virtual Storage

Postby Robert Sample » Mon Aug 16, 2010 4:42 pm

Terminology note: JCL does not do a VSAM delete / define. You can do it using IDCAMS (which is a utility executed in JCL), or third party vendor packages, but JCL per se cannot be used to create VSAM files.

You are mixing apples and oranges in your post.

Apples: "insufficient virtual storage" means the program you are executing ran out of memory. This is the REGION= parameter on either the JOB or EXEC statement. You need to consult your site support group, since sites can restrict memory usage by job class, job name, or site exit and there may be something specific to your site you need to do to get more memory.

Oranges: Talking about a VSAM file -- your program uses memory for the buffers to access the VSAM file, but the number of records has nothing to do with "insufficient virtual storage". 14 million 149-byte records requires 2,288,600,000 bytes of disk space. With what you have provided, we cannot tell you how big to make the CYLINDERS value in your IDCAMS DEFINE CLUSTER command since there are some other parameters that impact space -- CONTROLINTERVALSIZE and FREESPACE being the main ones. Defining the VSAM file with FSPC(50,50) would require a lot more space than defining it with FSPC(0,0) -- just as an example.
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Re: Virtual Storage

Postby NicC » Mon Aug 16, 2010 5:07 pm

Is your recordsize (LRECL) or blocksize (BLKSIZE) = 149? If your blocksize is 149 then consider adding a couple of zeros to the end - actually for a PS file define BLKSIZE=0 and let the system define it for you.

For VSAM, if the system is set up correctly you can actually allocate VSAM files through JCL but I would need to read the manuals to figure out how exactly. but CI size (VSAM equivalent of BLKSIZE) is vital and free space should not be set to 0!
The problem I have is that people can explain things quickly but I can only comprehend slowly.
Regards
Nic
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Re: Virtual Storage

Postby Robert Sample » Mon Aug 16, 2010 5:37 pm

free space should not be set to 0!
Nic: actually, this depends upon the application and what is being done with the VSAM file. For example, we have a VSAM file that is built to facilitate a report. The file is written once, never updated since it is rebuilt each day, and the data is read to create a file transferred to an external server. There is absolutely no reason in such a case to have free space -- without doing any adds or updates, there is no requirement for free space.
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Re: Virtual Storage

Postby steve-myers » Mon Aug 16, 2010 7:45 pm

In Mr. Sample's post, I have to wonder why VSAM was used at all! At first glance this is sequential data.

In the 1990s I worked at a site that used RMDS for report management; My 15+ year old memory is RMDS stashed the reports in VSAM datasets. It did such a wonderful job the site acquired IAM to use in place of VSAM for the report data sets. RMDS doctored the report data in the VSAM/IAM data sets to allow for much faster access to individual pages instead of sequentially reading the data. IAM was used because the VSAM data sets were allocated in cylinders, but generally used only a fraction of the space; IAM would allocate its data sets in track units. IAM was not used because of its alleged better performance. As far as I know all other VSAM use in the shop remained VSAM.
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Re: Virtual Storage

Postby Robert Sample » Mon Aug 16, 2010 7:55 pm

From the original post:
If I have a 14 million of records what could be its appropriate TRACKS or CYLINDER definition in jcl's delete define of a VSAM file?
I haven't been told enough yet to know whether sequential makes sense or not -- the original post specifically mentioned KSDS.
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Re: Virtual Storage

Postby boy_frame » Tue Aug 17, 2010 5:43 am

What shoulde be my CISIZE in this case.My file RECL = 149,Fixed blocked and KSDS.Thanks.
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Re: Virtual Storage

Postby dick scherrer » Tue Aug 17, 2010 6:34 am

Hello,

With what you have posted so far, we also cannot tell you what to use for CI Size. . .

This link is to a redbook you want to download and read - VSAM Demystified:

http://www.redbooks.ibm.com/abstracts/s ... .html?Open

Suggest you download the PDF version.
Hope this helps,
d.sch.
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Re: Virtual Storage

Postby Robert Sample » Tue Aug 17, 2010 6:47 am

What shoulde be my CISIZE in this case.My file RECL = 149,Fixed blocked and KSDS.Thanks.
There is no way we can answer that with what you have provided. The types of question that would need answering include:

-- is the access sequential, random, or a mix (and if a mix, how much random versus sequential)?
-- is the data set accessed by CICS?
-- what is the update pattern for the data set?
-- how much free space is needed, above and beyond the update pattern?
-- what are your site standards?

Terminology note: "fixed blocked" refers to a DCB, which does not apply to VSAM files. VSAM files have controlintervals, not blocks.
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