1. Administrator's Guide
  2. Library Management
  3. Automatic Recovery to Desired State

Automatic Recovery to Desired State

ACSLS now restores tape libraries and drives to the availability you desire. This is done by tracking both the current state and the desired state for ACSs, ports, LSMs, and tape drives. When a library or drive is no longer accessible by ACSLS or is inoperative, ACSLS changes its current state to offline. After the library or drive becomes accessible or operative again, ACSLS will automatically recover it and bring it back online if its desired state is online.

Current state and desired state

  • Desired state manages library and tape drive availability. Desired state is the availability that you want for an ACS, port connection, LSM, or tape drive. The initial desired state for all library components is online. You can set the desired state through an explicit vary command. (This is a vary from cmd_proc, the ACSLS GUI, or an ACSAPI client. It is not a vary that ACSLS internally generates because of a library status change.) The desired state for library components can be viewed using the query lmu and display commands.

  • The current state (specified as "state") for an ACS, port, LSM, or drive is the current availability of the component limited by desired state. Current state reflects whether a library component is ready and communicating, limited by the desired state of the component and higher level components.

    For example, if the desired state of an LSM is online but it is not ready, its current state is offline. When the LSM comes ready again, the library sends ACSLS a message, and ACSLS automatically recovers the LSM and brings its current state back online.

    However, if an LSMs' desired state is offline, ACSLS sets the current state to offline. If the LSM goes not ready and comes back to ready status, ACSLS will leave the LSMs' current state offline.

Current state cascades down, desired state does not

The current state of a library component cascades down to lower level components.

  • Specifically, if an ACS is no longer accessible, the current state of the ACS is offline. The current state of all LSMs and drives are also set to offline because they are also inaccessible.

  • When the desired state of an ACS is changed to offline by a vary command, the current state of the ACS is set to offline, and the current state of all LSMs and drives in the ACS are set to offline.

  • Likewise, when the current state of an LSM changes to offline, the current state of all drives in the LSMs become offline. The desired state of the drives does not change.

Changing the desired state of a library component does not affect the desired state of lower level components.

  • Changing the desired state of an ACS does not affect the desired state of the LSMs and drives in the ACS.

  • Changing the desired state of an LSM does not affect the desired state of the drives in the LSM.

  • This lets you vary selected drives in an LSM offline to make them inaccessible.You can then vary the LSM offline for maintenance. When you vary the LSM back online, the selected drives remain offline, while the other drives come back online.

Availability of physical libraries and drives affects logical libraries and drives.

  • The availability of logical libraries and tape drives in logical libraries is also governed by the desired state that you set for both the underlying physical library and the logical library.

  • If the desired states for both the physical library and logical library are online, the current states of logical libraries and logical tape drives reflect the current state of the underlying physical libraries and drives.

  • However, if the desired state for the physical ACS or drive is online, but the desired state of the logical library or drive is offline, the logical library or drive remains offline and unavailable.