After upgrading AIX 5.3 to TL12 SP6, no trunks are available for WebSphere Voice Response 4.2 systems.
The problem has impact for trunks configured with either DTNA, DTTA or DTXA adapters. This problem is caused by AIX defect IV25948 on 32 bit kernel.
AIX 5.3 is now End of Support. For WebSphere Voice Response customers with an AIX 5.3 Support Extension the fix is available from AIX TL12 SP07.