PM71710: "READ_UNCOMMITTED" SETTING FOR THE FETCH PLAN ISOLATION LEVEL IS IGNORED IN DB2DICTIONARY

8.5.0.2: WebSphere Application Server V8.5 Fix Pack 2
8.0.0.6: WebSphere Application Server V8.0 Fix Pack 6
8.0.0.7: WebSphere Application Server V8.0 Fix Pack 7
8.0.0.8: WebSphere Application Server V8.0 Fix Pack 8
8.0.0.9: WebSphere Application Server V8.0 Fix Pack 9
8.0.0.10: WebSphere Application Server V8.0 Fix Pack 10
8.0.0.11: WebSphere Application Server V8.0 Fix Pack 11
8.0.0.12: WebSphere Application Server V8.0 Fix Pack 12
8.0.0.13: WebSphere Application Server V8.0 Fix Pack 13
8.0.0.14: WebSphere Application Server V8.0 Fix Pack 14
8.0.0.15: WebSphere Application Server V8.0 Fix Pack 15

APAR status

• Closed as program error.

Error description

• When a user sets an isolation query hint of "READ_UNCOMMITTED"
  for DB2, this hint/isolation level is ignored and the default
  isolation level is used.
  

Local fix

Problem summary

• ****************************************************************
  * USERS AFFECTED:  All users of IBM WebSphere Application      *
  *                  Server V8.0.0 and V8.5.0 who make           *
  *                  use of "READ_UNCOMMITTED" isolation         *
  *                  level setting for an OpenJPA fetch          *
  *                  plan when using a DB2 dictionary.           *
  ****************************************************************
  * PROBLEM DESCRIPTION: "READ_UNCOMMITTED" isolation            *
  *                      level setting for the OpenJPA fetch     *
  *                      plan isolation level is ignored         *
  *                      in DB2Dictionary.                       *
  ****************************************************************
  * RECOMMENDATION:                                              *
  ****************************************************************
  Take the following JPA Query hint:
  Query query = EntityManager.createQuery(.....
  query.setHint("openjpa.FetchPlan.Isolation",
  "READ_UNCOMMITTED");
  When you set a query hint as shown above for DB2, no "with UR"
  clause is append to the query; the setting is completely
  ignored.
  

Problem conclusion

• With this fix, code has been added to OpenJPA to support a
  "READ_UNCOMMITTED" isolation level setting for the OpenJPA
  fetch plan. It should be noted that an uncommitted read is
  risky and should be avoid if possible. The JPA specification
  requires a minimum of read committed isolation to ensure that
  no "dirty reads" or "non-repeatible reads" can occur.  Use of
  "READ_UNCOMMITTED" isolation may cause data integrity
  problems.
  
  The fix for this APAR is currently targeted for
  inclusion in Service Levels (Fix Packs) 8.0.0.6 and
  8.5.0.2 of WebSphere Application Server versions 8.0.0 and
  8.5.0.
  
  Please refer to the recommended updates page for delivery
  information:
  http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

  PM80445

Fix information

• Fixed component name

  WEBS APP SERV N

• Fixed component ID

  5724H8800

Applicable component levels

• R800 PSY

     UP

• R850 PSY

     UP