VSAM LSR

[ess...@juno.com]

I have an application that has several VSAM datasets.
These datasets currently use NSR (Non Shared Resources).

The Application is written in assembler.
I want to switch some of the Files to use LSR.
If two files share a buffer pool do I need to concern my self with
the contents of the buffer pool or is the Access Method handling that.

In other words If I issue a VSAM GET for File A, is VSAM managing the contents of the LSR buffer pool with respect to the two files that may or may nor have records in the buffer pool ?

Do I need to use any additional Assembler VSAM macros to manage the
contents of the buffer pool ?

Paul D'Angelo

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[Chase, John]

> -----Original Message-----
> From: IBM Mainframe Discussion List On Behalf Of ess...@juno.com
>
> I have an application that has several VSAM datasets.
> These datasets currently use NSR (Non Shared Resources).
>
> The Application is written in assembler.
> I want to switch some of the Files to use LSR.
> If two files share a buffer pool do I need to concern my self with
> the contents of the buffer pool or is the Access Method handling that.

The access method handles the LSR buffering.

> In other words If I issue a VSAM GET for File A, is VSAM managing the
contents of the LSR buffer pool
> with respect to the two files that may or may nor have records in the
buffer pool ?
>
> Do I need to use any additional Assembler VSAM macros to manage the
> contents of the buffer pool ?

No.

-jc-

[Hal Merritt]

All good points. However, with batch LSR, a few simple JCL changes should do the trick. And, oddly enough, the defaults are almost always suitable.

-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-...@bama.ua.edu] On Behalf Of Larry Crilley
Sent: Monday, December 28, 2009 12:49 PM
To: IBM-...@bama.ua.edu
Subject: Re: VSAM LSR

The access method (VSAM) manages the buffer pool and buffer lookasides. You
just issue the GET(s).

You must build the LSR pool before the OPEN of each VSAM file. If the
datasets have different data/index CISIZES, you will need to build the pool
accordingly. Also, if these are KSDS (indexed) VSAM files, you should look
into building separate data and index LSR pools. Ideally, for the index,
you would want to build it large enough to hold the upper levels of the
index component plus a few for sequence set records.

Paul D'Angelo

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[John Kington]

Paul,

>I have an application that has several VSAM datasets.
>These datasets currently use NSR (Non Shared Resources).
>
>The Application is written in assembler.
>I want to switch some of the Files to use LSR.
>If two files share a buffer pool do I need to concern my self with
>the contents of the buffer pool or is the Access Method handling that.
>
>In other words If I issue a VSAM GET for File A, is VSAM managing the contents of the LSR buffer pool with respect to the two files that may or >may nor have records in the buffer pool ?
>
>Do I need to use any additional Assembler VSAM macros to manage the
>contents of the buffer pool ?

I believe someone else mentioned batch LSR but you could use system managed buffering if the vsam datasets are SMS managed. It would be even less work than implementing batch LSR. My testing showed very good results such that I would problably not bother to setup LSR in an assembler program again.

Regards,
John