Managing the Broker Persistent Store

The persistent store is used for storing unit-of-work messages to disk. This means message and status information can be recovered after a hardware or software failure to the previous commit point issued by each application component. Under BS2000, the broker persistent store can be implemented with the Adabas database of Software AG. This document covers the following topics:

See also Concepts of Persistent Messaging.


Implementing an Adabas Database as Persistent Store

Introduction

EntireX provides an Adabas persistent driver. This enables Broker unit of work (UOW) messages and their status to be stored in an Adabas file. It is designed to work with Adabas databases under z/OS, Linux, Windows and BS2000, and can be used where the database resides on a different machine to the Broker kernel. For performance reasons, we recommend using EntireX Broker on the same machine as the Adabas database.

Adabas Persistent Store Parameters

Parameters are supplied using the Adabas-specific Attributes in the platform-independent Administration documentation. See excerpt from the attribute file:

DEFAULTS=BROKER
  STORE                     = BROKER
  PSTORE-TYPE               = ADABAS
  PSTORE                    = COLD
DEFAULTS=ADABAS
  DBID                      = dbid
  FNR                       = fnr

Configuring and Operating the Adabas Persistent Store

Restrictions

If a HOT start is performed, the Broker kernel must be executed on the same platform on which also the previous Broker executed. This is because some portions of the persistent data are stored in the native character set and format of the Broker kernel. It is also necessary to start Broker with the same Broker ID as the previous Broker executed.

If a COLD start is executed, a check is made to ensure the Broker ID and platform information found in the persistent store file is consistent with the Broker being started (provided the persistent store file is not empty). This is done to prevent accidental deletion of data in the persistent store by a different Broker ID. If you intend to COLD start Broker and to utilize a persistent store file which has been used previously by a different Broker ID, you must supply the additional Adabas-specific attribute FORCE-COLD=YES.

Recommendations

  • Perform regular backup operations on your Adabas database. The persistent store driver writes C1 checkpoint records at each start up and shut down of Broker.

  • For performance reasons, execute Broker on the same machine as Adabas.

Broker Checkpoints in Adabas

During startup, Broker writes the following C1 checkpoint records to the Adabas database. The time, date and job name are recorded in the Adabas checkpoint log. This enables Adabas protection logs to be coordinated with Broker executions. This information can be read from Adabas, using the ADAREP utility with option CPLIST:

Broker Execution Name Broker Execution Type Adabas
ETBC Broker Cold Start Normal Cold Start
ETBH Broker Hot Start Normal Hot Start
ETBT Broker Termination Normal Termination

Adabas DBA Considerations

BLKSIZE: Adabas Persistent Store Parameter for Broker

Caution should be exercised when defining the block size (BLKSIZE) parameter for the Adabas persistent store. This determines how much UOW message data can be stored within a single Adabas record. Therefore, do not define a much larger block size than the size of the maximum unit of work being processed by Broker. (Remember to add 41 bytes for each message in the unit of work.) The advantage of having a good fit between the unit of work and the block size is that fewer records are required for each I/O operation.

It is necessary to consider the following Adabas parameters and settings when using Adabas for the persistent store file:

Table of Adabas Parameter Settings

Topic Description
Allowing Sufficient Adabas UQ Elements Allow sufficient Adabas user queue (UQ) elements each time you start Broker. The Broker utilizes a number of user queue elements equal to the number of worker tasks (NUM-WORKER), plus two. Adabas timeout parameter (TNAE) determines how long the user queue elements will remain. This can be important if Broker is restarted after an abnormal termination, and provision must be made for sufficient user queue elements in the event of restarting Broker.
Setting Size of Hold Queue Parameters Consideration must be given to the Adabas hold queue parameters NISNHQ and NH. These must be sufficiently large to allow Adabas to add/update/delete the actual number of records within a single unit of work.

Example: where there are 100 message within a unit of work and the average message size is 10,000 bytes, the total unit of work size is 1 MB. If, for example, a 2 KB block size (default BLKSIZE=2000) is utilized by the Adabas persistent store driver, there will be 500 distinct records within a single Adabas commit (ET) operation, and provision must be made for this to occur successfully.

Setting Adabas TT Parameter Consideration must be given to the Adabas transaction time (TT) parameter for cases where a large number of records is being updated within a single unit of work.
Defining LWP Size Sufficient logical work pool (LWP) size must be defined so that the Adabas persistent store can update and commit the units of work. Adabas must be able to accommodate this in addition to any other processing for which it is used.
Executing Broker Kernel and Adabas Nucleus on Separate Machines If Broker kernel is executed on a separate machine to the Adabas nucleus, with a different architecture and codepage, then we recommend running the Adabas nucleus with the UEC (universal conversion) option in order to ensure that Adabas C1 checkpoints are legible within the Adabas checkpoint log.
Setting INDEXCOMPRESSION=YES This Adabas option can be applied to the Adabas file to reduce by approximately 50% the amount of space consumed in the indexes.
4-byte ISNs If you anticipate having more than 16 million records within the persistent store file, you must use 4-byte ISNs when defining the Adabas file for EntireX.
Specification of Adabas LP Parameter
Warning:
This parameter must be specified large enough to allow the largest UOW to be stored in Adabas.

If this is not large enough, Broker will detect an error (response 9; subresponse - 4 bytes - X'0003',C'LP') and Broker will not be able to write any further UOWs.

See the description of the LP parameter under ADARUN Parameters in theDBA Reference Summary of the Adabas documentation.

Tips on Transports, Platforms and Versions

  • Entire Net-Work
    If you intend to use Adabas persistent store through Entire Net-Work, see the Entire Net-Work documentation for installation and configuration details.

  • Adabas Versions
    Adabas persistent store can be used on all Adabas versions currently released and supported by Software AG.

  • Prerequisite Versions of Entire Net-Work with Adabas
    See the Adabas and Entire Net-Work documentation to determine prerequisite versions of Entire Net-Work to use with Adabas at your site.