DASD I/O errors may occur when log data is being duplexed to DASD
staging data sets. When this occurs, system logger tries to recover
by doing the following:
- Offload current log data to DASD log data sets.
- Delete and unallocate the staging data set.
- Re-allocate a new instance of the staging data set.
In the meantime, system logger continues to accept write and other
requests against the log stream.
If system logger cannot re-allocate a new staging data set, the
I/O error is characterized as unrecoverable. In the case of an unrecoverable
staging data set I/O error, system logger does the following:
- For a coupling facility based log stream,
system logger switches the duplexing mode to duplex log data to local
storage buffers. The system issues message IXG255I indicating that
the duplexing mode has changed. Normal system logger processing continues.
The log stream may be more vulnerable to data loss due to system,
sysplex, or coupling facility failure.
- For a DASD-only log stream, system logger
disconnects connectors from the log stream. The system issues message
IXG216I to indicate that connectors are being disconnected because
a staging data set could not be allocated.