VMS Help  —  RMU72  Restore  Command Qualifiers, Loader Synchronization
    Loader_Synchronization

    Allows you to preload tapes in order to minimize the need for
    operator support. When you specify the Loader_Synchronization
    qualifier and specify multiple tape drives, the restore operation
    reads from the first set of tape volumes concurrently, then waits
    until all concurrent tape operations conclude before assigning
    the next set of tape volumes. This ensures that the tapes can be
    loaded into the loaders or stackers in the order required by the
    restore operation.

    The Loader_Synchronization qualifier does result in reduced
    performance. For maximal performance, no drive should remain
    idle, and the next identified volume should be placed on the
    first drive that becomes idle. However, because the order in
    which the drives become idle depends on many uncontrollable
    factors and cannot be predetermined, the drives cannot be
    preloaded with tapes.

    Because the cost of using the Loader_Synchronization qualifier is
    dependent on the hardware configuration and the system load, the
    cost is unpredictable. A 5% to 20% additional elapsed time for
    the operation is typical. You must determine whether the benefit
    of a lower level of operator support compensates for the loss of
    performance. The Loader_Synchronization qualifier is most useful
    for large restore operations.

    The Loader_Synchronization qualifier has no effect unless you
    specify the Volumes qualifier also.
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