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


Chapter 5 Processing External DBMS Data : Synchronization and Recovery

Synchronization and Recovery
Transaction Synchronization
A transaction in the external DBMS spans the same length of time as a TIBCO Object Service Broker transaction. The BROWSE/NOBROWSE flag on the workbench determines the locks taken on external data.
A COMMIT causes the external DBMS to release all locks and close all cursors. COMMITs are issued by the TIBCO Object Service Broker Gateway at the end of a transaction even if no updates are made so locks taken are released.
Intermediate COMMITs in NOBROWSE transactions, while any updates to SLK tables are pending, could be allowed depending on the setting of the INTCOMMIT configuration parameter (refer to INTCOMMIT).
The Oracle Gateway preserves all open cursors beyond a COMMIT point. The ODBC Gateway preserves, as well, all open cursors when connected to Oracle, MS SQL Server, and DB2 UDB. Cursor stability is not guaranteed for other possible data sources.
An intermediate COMMIT, if propagated into the target DBMS, can compromise transactional integrity and, therefore, should be used with care.
Normally, all locks acquired prior to a COMMIT are released by the target DBMS (except those used implicitly by the cursors currently open); accordingly, a TIBCO Object Service Broker transaction should not rely on locks between commit points and on the durability of updates throughout its lifetime.
Synchronization Results
If updates are performed, the following results occur for the following requests:
The Gateway issues COMMIT. Subsequent requests for data are considered erroneous.
The Gateway issues ROLLBACK. Subsequent requests for data are considered erroneous.
If no updates are performed, the following requests have these results:
The Gateway does not receive ROLLBACK if there is no update.
The exception COMMITLIMIT does not apply to SLK tables. Requests to update external data are processed as they are encountered and are not buffered in the intent list.
Transaction Recovery
Updating External Data Only
Transactions that update only external data are recoverable under the external DBMS.
Updating TIBCO Object Service Broker and External Data
Fail Safe level‑1 processing provides a method of ensuring data integrity when a TIBCO Object Service Broker transaction updates both external and TIBCO Object Service Broker data in the same transaction. If you do not request Fail Safe processing, transactions that update both external and TIBCO Object Service Broker data can result in discrepancies if the Gateways or the Data Object Broker abnormally terminates during transaction end processing. Refer to Implementing Fail Safe Processing for more information.
Recovering from an Abnormal Data Object Broker Shutdown
The Gateways do not automatically log in to a Data Object Broker that is reactivated after an abnormal Data Object Broker shutdown.

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