Natural Global Buffer Pool under z/OS

This document describes purpose and usage of a Natural global buffer pool (GBP) under the operating system z/OS.

The section covers the following topics:

Certain parts of the Natural global buffer pool are identical under z/OS and z/VSE. These parts are concentrated in a separate section (see Common GBP Operating Functions under z/OS and z/VSE) which covers the following topics:

Using a Natural Global Buffer Pool

Purpose

The Natural global buffer pool is a segment of storage assigned from the z/OS extended common system area (ECSA) above 16 MB (or from CSA storage below, if requested), used by Natural to load and execute Natural programs.

Benefits

Using a global buffer pool, multiple Natural sessions under different TP monitors (multiple copies of CICS, TSO, IMS TM, etc.) and/or in multiple batch sessions share the same area - thus requiring less storage than would be required for a local buffer pool in each environment.

Prerequisites

The following prerequisites must be met if you want to use a global buffer pool:

  1. The module NATGBPvr must have been linked into an Authorized Program Facility (APF) library; see the corresponding step in Installing Natural on z/OS in the Installation for z/OS documentation.

  2. The global buffer pool must have been started; see the corresponding step in Installing Natural on z/OS in the Installation for z/OS documentation.

Operating the Natural Global Buffer Pool

The global buffer pool is operated using the program NATGBPvr which must be executed from within an Authorized Program Facility (APF) library.

The following topics are covered below:

Note:
In the following document, vrs or vr represents the relevant version of the product. For information on product versions, see Version in the Glossary.

Allocation of the Natural GBP

If the z/OS parameter ALLOWUSERKEYCSA(YES) has explicitly been specified in SYS1.PARMLIB(DIAGxx), a Natural global buffer pool is allocated in user key, so that Natural sessions accessing a global buffer pool have write permission for that buffer pool.

If ALLOWUSERKEYCSA(NO) is in effect, a Natural global buffer pool is allocated in system key; therefore, Natural sessions accessing a global buffer pool do not have any write permission for that buffer pool. These Natural sessions call the Authorized Services Manager (ASM) to perform all buffer pool functions. As a consequence, installation of the ASM is mandatory. The ASM is not only called to load a Natural object into the buffer pool but also to maintain the use count of a Natural object if the execution of this Natural object is started or terminated. The calls to the Authorized Services Manager will increase Natural’s resource consumption. The overhead is hard to predict and depends on the application profile (ratio of program calls to program execution time).

Setting up the Natural GBP

The functions provided by the operating program NATGBPvr are activated in that they are

  • specified in a parameter card (PARM=),

  • read from a file (see below),

  • or supplied by the MODIFY operator command.

NATGBPvr expects the first command in the parameter field (PARM=) of the EXEC statement.

You may enter:

  • one of the functions (described in the section Common GBP Operating Functions under z/OS and z/VSE)

  • or a reference to an input file with CF=dd-name, where dd-name represents a DD name defined in the JCL. Only "card image" files are supported, that is, RECFM=F,LRECL=80, and only the first 72 bytes of the input record are honored. Every record included from the input file represents a command. Blank records or records prefixed with an asterisk (*) are ignored. A file is processed until End-Of-File (EOF). Example: PARM='CF=SYSIN1'

If the parameter field is not supplied or blank, the commands will be read from file SYSIN by default.

It is only possible to enter one function at a time at the console or one function per line using the command file, otherwise an error message will be returned.

Each command received, from the parameter card, from file input or from operator console input is shown on the operator console.

Starting the Natural GBP Operating Program

To start the program NATGBPvr, either start a started task or submit a job, which executes NATGBPvr.

Important:
To ensure that the global buffer pool is retained after a system failure, the global buffer pool should be started automatically during machine IPL.

Stopping the Natural GBP Operating Program

After all commands are processed, the program NATGBPvr terminates, unless

  • RESIDENT=Y was specified

  • or a buffer pool with a cache was created.

NATGBPvr will return one of the following condition codes:

Condition Code Explanation
0 All functions executed successfully.
20 An error has occurred; see the message log for details.

Sample NATGBPvr Execution Jobs

The following examples show sample batch jobs for creating and terminating a global buffer pool.

In the following examples, the notation vrs or vr represents the relevant product version. For information on product versions, see Version in the Glossary.

Example 1:

//GBPSTART JOB 
//*
//* Starts a global buffer pool with the name NATvrGBP, a size of 1 MB and
//* a text block size of 4 KB. The global buffer pool is allocated above 16 MB.
//* The subsystem used is NATv. 
//* After the allocation, the job GBPSTART terminates.
//* 
//STEP EXEC PGM=NATGBPvr,PARM='BPN=NATvrGBP,N=(1M)'
//SETPLIB DD DISP=SHR,DSN=USER.APF.LINKLIB

Example 2:

//GBPRES JOB 
//* 
//* Starts a global buffer pool with the name GBP, a default size of
//* 100 KB and a text block size of 1 KB. The global buffer pool is allocated
//* below 16 MB. The subsystem used is SAGS. 
//* After the allocation, the job GBPRES will wait for further commands.
//* Further commands may be entered using the MODIFY operator command: 
//* F GBPRES,command-string
//* 
//STEP EXEC PGM=NATGBPvr,PARM='BPN=GBP,N=(,BL,1),S=SAGS,R=Y'

Example 3:

//GBPSTOP 
//* 
//* Stops the global buffer pool GPB if it contains no active objects. If it
//* does contain active objects, the operator console will prompt for a reply.
//* Depending on the reply, the shutdown will be forced (Y) or aborted (N).
//* The subsystem used is NATv.
//* 
//STEP EXEC PGM=NATGBPvr,PARM='FSHUT,BPN=GPB'

Example 4: 

//GBPSTRT2 
//* Read commands from SYSIN1:
//* 
//* Start two global buffer pools (subsystem ID Nvrs) with names
//*   NATGBP1 - size=1024KB and a cache with size 2048KB, and
//*   NATGBP2 - size=2048KB without cache.    
//* Display all buffer pools of subsystem ID Nvrs.
//* 
//* Note: The job does not terminate by itself, but stays resident and waits
//*       for operator commands because it owns the data space allocated for
//*       buffer pool NATGBP1.
//*
//* To shut down the buffer pools, send the operator command MODIFY with
//* parameter CF=SYSIN2 to execute the corresponding FSHUTs. 
//*
//STEP EXEC PGM=NATGBPvr,PARM='CF=SYSIN1'
//SYSIN1  DD *
CREATE,BPN=NATGBP1,S=Nvrs,N=(1M),BPC=2M
CREATE,BPN=NATGBP2,S=Nvrs,N=(2M)
SHOWBP S=Nvrs
//SYSIN2 DD *
FSHUT,BPN=NATGBP1,S=Nvrs
FSHUT,BPN=NATGBP2,S=Nvrs
SHOWBP S=Nvrs  
//*

Localization

The module NATGBPTX is delivered in source form. It contains all error messages in English in mixed case. The messages can be translated into other languages as required. In this case, the "new" NATGBPTX source module has to be assembled and the module NATGBPvr has to be relinked.

To issue the global buffer pool messages including their variable parts in upper case, the global buffer pool parameter module NATGBPRM has to be assembled with the UCTRAN parameter set to YES, and the module NATGBPvr has to be relinked.

To relink the module NATGBPvr, use the following JCL: 

//SYSLIN  DD *
SETCODE AC(1)
SETOPT PARM(REUS=RENT)
INCLUDE NATLIB(NATGBPMG) 
INCLUDE SMALIB(NATGBPRM) 
INCLUDE SMALIB(NATGBPTX)
INCLUDE NATLIB(NATBPMGR)
NAME NATGBPvr(R)
/*

Messages

Refer to Natural Global Buffer Pool Manager Messages in the Natural Messages and Codes documentation