Like a coupling facility log stream, a DASD-only log stream is subject to system or system logger failure. A DASD-only log stream is not subject, however, to coupling facility or structure failures. When a failure occurs involving a DASD-only log stream, system logger releases the exclusive ENQ on the log stream name serializing the log stream for one system. No system-level or peer recovery is performed for a DASD-only log stream after a failure or as part of system initialization. System logger does not perform system-level recovery for a DASD-only log stream because data is already safeguarded on DASD staging data sets, a non-volatile medium. For a DASD-only log stream, offload of log data to DASD log data sets is not done as part of recovery processing for the same reason - log data is already on DASD staging data sets. Peer recovery is both unnecessary and not possible for a DASD-only log stream, because there are no peer systems connected to the log stream.
Recovery for a DASD-only log stream only takes place when an application reconnects to the log stream. As part of connect processing, system logger reads log data from the staging data set (associated with the last connection to the log stream) into the local storage buffers of the current connecting system. This allows the application to control recovery, by selecting which system they wish to have reconnect to the log stream and when. Note that for another system to connect to the log stream and perform recovery, the staging data sets must reside on devices accessible by both systems.