2013-06-13T03:43:18.623Z [7FFFF3B09700 error 'Default'] [Vdb::LockRepositoryHelper] SQLExecDirect failed: 57011:-438:ODBC error: (57011) - [IBM][CLI Driver][DB2/LINUXX8664] SQL0438N Application raised error or warning with diagnostic text: "Error deleting from VPX_SESSIONL". SQLSTATE=57011
2013-06-13T03:43:19.646Z [7FFFF3B09700 error 'Default'] [Vdb::LockRepositoryHelper] SQLExecDirect failed: 57011:-438:ODBC error: (57011) - [IBM][CLI Driver][DB2/LINUXX8664] SQL0438N Application raised error or warning with diagnostic text: "Error deleting from VPX_SESSIONL". SQLSTATE=57011
The below KB should help
http://kb.vmware.com/kb/2030601
A better solution would be to upgrade the appliance to atleast 5.0 Update 2 that uses the PostgresSQL DB and these issues (IBMDB2) are resolved
Upgrade the VMware vCenter Server Appliance
<snip>
Version 5.0.1 of the vCenter Server Appliance uses PostgreSQL for the embedded database instead of IBM DB2, which was used in vCenter Server Appliance 5.0. If you use the embedded database with the vCenter Server Appliance, when you upgrade from version 5.0 to version 5.0.1, the embedded IBM DB2 database is migrated to a PostgreSQL database. The configuration state of your existing database is preserved and the schema is upgraded to be compatible with vCenter Server Appliance 5.0.1.
</snip>