Recovering from conversation failure
A VTAM® APPC or TCP/IP conversation might fail during or after allocation. The conversation is not available for use until you recover from the situation.
Symptoms
VTAM or TCP/IP returns a resource-unavailable condition along with the appropriate diagnostic reason code and message. A DSNL500 or DSNL511 (conversation failed) message is sent to the console for the first failure to a location for a specific logical unit (LU) mode or TCP/IP address. All other threads that detect a failure from that LU mode or IP address are suppressed until communications to the LU that uses that mode are successful.Db2 returns messages DSNL501I and DSNL502I. Message DSNL501I usually means that the other subsystem is not operational. When the error is detected, it is reported by a console message, and the application receives an SQL return code.
If you use application-directed access or DRDA as the database protocols, SQLCODE -30080 is returned to the application. The SQLCA contains the VTAM diagnostic information, which contains only the RCPRI and RCSEC codes. For SNA communications errors, SQLCODE -30080 is returned. For TCP/IP connections, SQLCODE -30081 is returned.
Environment
The application can choose to request rollback or commit, both of which deallocate all but the first conversation between the allied thread and the remote database access thread. A commit or rollback message is sent over this remaining conversation.
Errors during the deallocation process of the conversation are reported through messages, but they do not stop the commit or rollback processing. If the conversation that is used for the commit or rollback message fails, the error is reported. If the error occurred during a commit process and if the remote database access was read-only, the commit process continues. Otherwise the commit process is rolled back.
Diagnosing the problem
System programmer response: Review the VTAM or TCP/IP return codes, and possibly discuss the problem with a communications expert. Many VTAM or TCP/IP errors, besides the error of an inactive remote LU or TCP/IP errors, require a person who has a knowledge of VTAM or TCP/IP and the network configuration to diagnose them.
Resolving the problem
Operator response: Correct the cause of the unavailable-resource condition by taking the action that is required by the diagnostic messages that are displayed on the console.