The Asynchronous Operations Manager (AOM) manages the interface
to the host for the control operations performed by the 3990 Storage
Control, the IBM® TotalStorage Enterprise
Automated Tape Library (3494), and the 3495 Tape Library Dataserver.
AOM performs the following functions:
- Issues two types of control operations:
- Synchronous I/O operations—those I/O operations that are
complete when the host receives both channel end and device end.
- Asynchronous I/O operations—those operations that are not
complete when the host receives both channel end and device end. The
following takes place to complete an asynchronous operation:
- The operation is validated.
- The storage control sends channel end and device end to the host.
- The storage control performs the operation.
- Optionally, the storage control raises an attention interrupt
to the host, signalling that the operation is complete.
- The host processes the attention message to determine the operations
status.
- Processes attention interrupts from the storage control to the
host, notifying the host when certain asynchronous operations complete.
- Processes device state transition interrupts from the storage
control to the host notifying all attached hosts when the subsystem
or a device changes status. The storage control sends a device state
transition interrupt to the host. This interrupt is unsolicited status
of attention, device end, and unit exception. (A control unit end
or busy might also be merged into this status.)