Reserving and releasing shared tape drives

This reservation is held until an application releases it, or the node is removed from the cluster:

• When the special file for the tape is closed, the default action is to release the tape drive. An application can open a tape drive with a do-not-release-on-close flag. PowerHA® SystemMirror® will not be responsible for maintaining the reservation after an application is started.
• Upon stopping cluster services on a node and bringing resource groups offline, the tape drive is released, allowing access from other nodes.
• Upon unexpected node failure, a forced release is done on the takeover node. The tape drive is then reserved as part of resource group activation.

Setting tape drives to operate synchronously or asynchronously

If a tape operation is in progress when a tape reserve or release is initiated, it may take might minutes before the reserve or release operation completes. PowerHA SystemMirror allows synchronous or asynchronous reserve and release operations. Synchronous and asynchronous operation is specified separately for reserve and release.

Synchronous operation

With synchronous operation, (the default value), PowerHA SystemMirror waits for the reserve or release operation, including the execution of a user-defined recovery procedure, to complete before continuing.

Asynchronous operation

With asynchronous operation, PowerHA SystemMirror creates a child process to perform the reserve or release operation, including the execution of a user-defined recovery procedure, and immediately continues.