Copyright © TIBCO Software Inc. All Rights Reserved
Copyright © TIBCO Software Inc. All Rights Reserved


Chapter 2 Operating the Service Gateway for IMS/DB : Implementing Fail Safe Processing

Implementing Fail Safe Processing
Fail Safe level‑1 processing guarantees consistency when updating both TDS and IMS data from a single instance of the Gateway in a single transaction. At the end of a transaction, the Data Object Broker requests that the Gateway commit outstanding updates. As part of IMS commit processing, the Gateway updates an IMS transaction database to record the successful commit. If the Gateway does not respond to the Data Object Broker in a reasonable amount of time, the transaction is flagged as being in doubt. Locks held on TDS data remain in place until the problem is resolved.
When a connection is re-established between the Data Object Broker and a Gateway with the same configuration as the one that failed, the Data Object Broker asks the Gateway if the in-doubt transaction completed. The Gateway checks the IMS transaction database to determine this. If the update is completed in IMS, the TDS updates are applied and the locks are released.
You can resolve only in-doubt transactions by starting an instance of Gateway with exactly the same parameter settings as the Gateway in use at the time the transaction was placed in doubt.
See Also
TIBCO Object Service Broker for z/OS Managing Backup and Recovery for more information on Fail Safe processing.
Procedural Overview
To implement Fail Safe level‑1 processing, you must:
1.
2.
3.
4.
These tasks are described in the following sections.
 
Task A Define an IMS transaction database
Member XIMSTRXD exists in the CNTL data set. Modify this member as explained in the USAGE section at the top of the member. The transaction database holds a maximum of one segment occurrence for each combination of the Gateway and a Data Object Broker.
Task B Define a PCB for the transaction database in each Gateway PSB
Member XIMSTRXP exists in the CNTL data set. Modify this member as explained in the USAGE section at the top of the member.
Task C Define a TIBCO Object Service Broker IMS transaction table
After defining an IMS transaction database, you must extract and load the transaction database into TIBCO Object Service Broker. When this is completed, you must define a TIBCO Object Service Broker IMS transaction table that points to the IMS transaction database. The default name for this table is @IMSFSTRXDB.
Task D Modify the Gateway Fail Safe startup parameters
Ensure that the following Gateway startup parameters are included in your Gateway startup JCL:
TRXDB=IMS.DBname
For more information on these Gateway startup parameters, refer to Supplying Gateway Startup Parameters.
At startup, the Gateway asks the Data Object Broker for the TIBCO Object Service Broker IMS transaction table definition specified in the FSTABLENAME gateway startup parameter. This table definition is bound for the life of the Gateway and is used at transaction end to update the IMS transaction ID database.
The transaction table can be managed in TIBCO Object Service Broker like any other IMS table. For example, you can write a TIBCO Object Service Broker rule to clean up the Fail Safe database when shutting down the Gateway.

Copyright © TIBCO Software Inc. All Rights Reserved
Copyright © TIBCO Software Inc. All Rights Reserved