Informix XA data sources incur frequent and varied database exceptions
 Technote (troubleshooting)
 
Problem(Abstract)
XA connections to databases that run on IBM® Informix® Dynamic Server, Versions 9.4 and 10.0, can undergo isolation level changes during global transactions. User-configured isolation level settings switch to database default settings and Informix Dynamic Server enforces this switch. The default isolation level that Informix uses depends upon one of the following database logging configurations:

  • If the logging type is not ANSI-compliant, Informix uses Read Committed as the default isolation level.

  • If the logging type is ANSI-compliant, Informix uses Serializable (called Repeatable Read in SET ISOLATION) as the default isolation level.


These switches in transaction isolation levels can cause the following problems for your application:

  • A java.sql.SQLException with the"Could not position within a table" error message.

  • Frequent database deadlock exceptions.

  • Frequent occurrences of database lock time-out expiration.

  • Transaction rollbacks and, in the worst-case scenario, data corruption. These situations occur due to the order of the create, update, and delete operations that produce inaccurate values or unsupported values.

 
Cause
Informix resets the transaction isolation setting to the database default when the XA transaction ends. Because the change occurs on the database side of a Java™ Database Connectivity (JDBC) connection, IBM WebSphere® Application Server does not detect the change. Therefore, the Application Server might not reset the transaction isolation level from the database default to the user-configured setting the next time that the affected connection is retrieved from the pool.
 
Resolving the problem
Use a version of Informix that incorporates the PTS 173076 fix. These versions are:
  • Informix Dynamic Server Version 10.00.xC4
  • Informix Dynamic Server Version 9.40.xC8
 
Related information
Access intent: isolation levels and update locks
Isolation level and resource reference
V6.02 Information Center Release Notes page
 
 
Cross Reference information
Segment Product Component Platform Version Edition
Application Servers WebSphere Application Server DB Connections/Connection Pooling AIX 5.1, 5.0.2 Enterprise
Application Servers Runtimes for Java Technology Java SDK
 
 


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > DB Connections/Connection Pooling
Operating system(s): AIX
Software version: 6.0.2
Software edition:
Reference #: 1210851
IBM Group: Software Group
Modified date: May 24, 2006