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 Linux, the broker persistent store can be implemented with:
the Adabas database of Software AG
the c-tree © database of FairCom Corporation ®
This document covers the following topics:
See also Concepts of Persistent Messaging.
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.
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
The Adabas Persistent Store driver module is contained within the
regular Broker load library or binaries directory. The module adapsi is activated by
specifying the PSTORE-TYPE parameter as shown above.
Use the supplied script persistence.fdu in the bin directory to create a persistent store file in your Adabas database. This script uses the Adabas FDT definition found in file persistence.fdt in the etc directory.
The script persistence.fdu can be executed like this:
persistence.fdu <dbid> <fnr>
Note:
You can customize the supplied script and FDT file in accordance
with your site requirements. See the Adabas Utilities
manual where necessary, specifically ADAFDU (File Definition Utility).
To run the script file
Ensure that you execute the script file on the same machine that the target Adabas is running on. (The database can be either active or inactive at the time you execute it.)
Ensure that Adabas environment variables (such as ACLDIR, ADATOOLS, ADABIN
and ADALNK) are set up. These environment variables are set
by sourcing the corresponding environment scripts. See your Adabas documentation for details.
Set your working directory to the one where the fdt file is located.
Execute the fdt file, passing it two parameters. (The first one is the DBID, where persistent store file is to be created; the second is the file number.)
Option: If the DBID is less than 3 characters long, include leading zeros. For example:
persistence.fdu 001 19
Result: Creation of file number 19 in database 1.
ADACMP FNDEF='01,WK,21,A,DE' ADACMP FNDEF='01,WJ,126,B,MU' ADACMP FNDEF='01,WI,126,B,DE,NU' ADACMP FNDEF='01,WL,96,A,DE,NU' ADACMP FNDEF='01,WP,96,A,DE,NU'
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 PSTORE-TYPE parameter FORCE-COLD=Y.
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.
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 |
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:
| 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.
Use either the Adabas utility
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| 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 |
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| 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.
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| 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.
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| 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.
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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 |
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 |
To calculate the Adabas file size it is necessary to estimate the number of records being stored. As an approximate guide, there will be one Adabas record (500 bytes) for each unprocessed unit of work, plus also n records containing the actual message data, which depends on the logical block size and the size of the unit of work. In addition, there will be one single record (500 bytes) for each unit of work having a persisted status.
Always allow ample space for the Adabas persistent store file since the continuous operation of Broker relies of the availability of this file to store and retrieve information.
Note:
If the Adabas file space is exceeded, Broker will
automatically terminate, and it will be necessary either to increase the space
available to the file using Adabas utilities or to perform a Broker HOT start
with NEW-UOW-MESSAGES=NO to allow units of work to be consumed
before normal operation can continue.
In this example there are 100,000 Active UOW records at any one time. Each of these is associated with two message records containing the message data. UOW records are 500 bytes in length. Each message record contains 2,000 bytes. In addition, there are 500,000 UOW status records residing in the persistent store, for which the UOW has already been completely processed. These are 500 bytes long.
Note:
The actual size of the data stored within the UOW message records is
the sum of all the messages within the UOW, plus a 41-byte header for each
message. Therefore, if the average message length is 59 bytes, the two 2,000
bytes, messages records, could contain n = 4,000 / (59+41), or 40 messages.
Adabas is assumed to compress the message data by 50% in the example (this can
vary according to the nature of the message data).
3-byte ISNs and RABNs are assumed in this example. A device type of 8393 is used; therefore, the ASSO block size is 4,096, and DATA block size is 27,644. Padding factor of 10% is specified.
The following example calculates the space needed for Normal Index (NI), Upper Index (UI), Address Converter (AC) and Data Storage (DS).
| Calculation Factors | Required Space |
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| Entity Requiring Space | Total Required Space |
| Normal Index (NI) | = 23,868 blocks |
| Upper Index (UI) | = 512 blocks |
| Data Storage (DS) | = 14,068 blocks |
| Address Converter (AC) | = 587 blocks |
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.
The DBA can perform an UNLOAD of the Adabas file in which the
persistent store is located (this must be done when Broker is not running).
This allows the persistent store to be LOADed into another Adabas file, in the
same or in another Adabas database. Broker can then be restarted (PSTORE=HOT)
with the attributes specifying the new location of the persistent store file.
See Table of Adabas Parameter Settings above.
See separate Adabas documentation for details of Adabas utilities for UNLOAD and LOAD operations.
The persistent store file can only be reloaded into another Adabas database running on the same platform type as the Adabas database from which it was unloaded.
EntireX provides a c-tree© persistent driver based on the c-tree© User API of the FairCom Corporation®. This driver manages a fast and reliable embedded local database.
In order to operate EntireX using the c-tree persistent store
option, you must assign Broker attribute
PSTORE-TYPE=CTREE. No other attributes are
required. However, several attributes are supported to set additional optional
attributes for the c-tree store. See c-tree-specific Attributes for details.
