Expired log stream token

There are conditions that will cause a log stream connection token to no longer be valid. This means that the unique log stream connection identifier, or the STREAMTOKEN, is no longer considered valid by system logger and the application receives an "expired log stream token" error response (refer to IxgRsnCodeExpiredStmToken in IXGCON macro) for Logger service requests using a stream token as input.

An expired log stream token can be the result of an application explicitly or implicitly disconnecting from a log stream, or it can be the result of an action within system logger from either the CFRM policy, system environmental conditions, or from internal or system logger component errors. When an application encounters an "expired stream token" condition unexpectedly, then it should re-connect to the log stream and obtain a valid stream token before making any subsequent Logger service requests.

An expired log stream can occur under the following conditions:

The log stream connector disconnects from the log stream by issuing an IXGCONNREQUEST=DISCONNECT,STREAMTOKEN=xstreamtoken and then issues another system logger services attempting to use the same STREAMTOKEN value.
The task (represented by a TCB or Task Control Block) that connected to the log stream terminates. This is often a problem that surfaces early in the coding of an application. Typically the application creates an initialization task to obtain resources. That task connects to the log stream, stores the log stream in persistent storage, and then terminates.
Because in this situation the "owning" task ended (through an end-of-task resource management operation), system logger automatically disconnects from the log stream. The correction for this is to connect to the log stream from a task that does not terminate until the log stream is no longer needed.
Any job step task (JST) terminates within the address space that has a connection to the log stream. System logger treats any job step task termination in a manner similar to an address space termination. That is, all log stream connections are disconnected and logger associations are terminated with the address space.
If this condition occurs and there remains an expected use of a log stream, a new log stream connection will be required.
Based on how and where the log stream token is maintained in the connector's storage, the system might pass an incorrect log stream to system logger. If the incorrect log stream token meets the format expected by system logger, then a return code X'04', reason code X'82D' (IxgRsnCodeExpiredStmToken) condition is returned. Otherwise, the incorrect log stream token results in the return code X'08', reason code X'806' (IxgRsnCodeBadStmToken) condition.

An expired log stream token not caused by application can occur under the following conditions:

For coupling facility log streams, that you are not currently using, Logger can also disconnect a requestor when certain structure failure conditions occur.
After an I/O or access error occurs for a staging data set, if system logger is unable to allocate a new data set for DASD-only log streams, system logger automatically disconnects the log stream.
System logger disconnects all connectors on the target system as a result of an operator SETLOGR FORCE,DISConnect,LSN=logstreamname command.
When the system logger address space terminates and is restarted while the log stream connector was persistent (that is the application address space and connecting task remained intact) then any subsequent use of a log stream token obtained before system logger terminated would be considered expired.
Severe error conditions can also occur within the Logger component that might cause the log stream to be disconnected unexpectedly.

Note that system logger will not disconnect a connector for log stream offload data set allocation errors or data set "full" conditions. The allocation of log stream offload data sets does not result in an "expired log stream token" condition.