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Managing an Optical Library

IP.com Disclosure Number: IPCOM000101287D
Original Publication Date: 1990-Jul-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 4 page(s) / 152K

Publishing Venue

IBM

Related People

Freeman, HL: AUTHOR [+3]

Abstract

Described is a method of managing an optical library that provides both performance advantages and programming consistency. The cornerstone of this library management implementation is a high-level command set used by all library resource requestors regardless of differences in the underlying library and drive hardware. Utilization of the library resources (optical drives, cartridge storage slots, and the robotics arm) is optimized for maximum optical subsystem throughput allowing multiple requests to be executed simultaneously from one or more requestors.

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This is the abbreviated version, containing approximately 49% of the total text.

Managing an Optical Library

       Described is a method of managing an optical library that
provides both performance advantages and programming consistency.
The cornerstone of this library management implementation is a
high-level command set used by all library resource requestors
regardless of differences in the underlying library and drive
hardware.  Utilization of the library resources (optical drives,
cartridge storage slots, and the robotics arm) is optimized for
maximum optical subsystem throughput allowing multiple requests to be
executed simultaneously from one or more requestors.

      An optical library contains storage slots for optical
cartridges, one or more optical drives for accessing or updating the
data on the cartridges, and a robotics mechanism for moving the
cartridges within, in to, and out of, the library.  These resources
must be effectively, reliably, and consistently managed to ensure the
best possible optical subsystem performance.  This library management
methodology implements a high-level command set to simplify access to
library and optimize resource utilization.

      A single entity controls all resources (drives, storage slots,
and robotics) within the library.  This Library Manager accepts
unique high-level commands that allow access to all resources within
the library.  These commands allow requestors to access LOGICAL
resources within the library without having to deal with each
device's PHYSICAL characteristics and subcommand formats.  The
library manager maps these logical resource requests to the specific
subcommand sequences accepted by the particular drive or library.
This library management implementation provides a consistent
interface to resource requestor, allows library robotics and drive
commands to execute concurrently, acts as the primary level of error
recovery processing, and concurrently manages multiple resource
requests.

      A high-level command set is implemented to simplify the
interface the requestor uses to access the optical library. For
example, a single high-level command "FLIP" replaces the optical
drive and library subcommand sequence "Stop Drive, Flip, Start
Drive".  The requestor simply issues the command and is posted when
the command completes. All drive and library interaction, including
attempting recovery from error conditions in the library or optical
drives, is handled within the Library Manager.  A complete list of
the high-level commands and their resulting device subcommand
sequences is shown in Fig 1.

      Subcommands to the optical drives and to the library robotics
are overlapped.  This increases optical subsystem throughput by
reducing the time required to execute each subcommand instruction
sequence.  An example of an overlapped subcommand sequence is
described below and depicted in Fig. 2.

      A request (R1) is received to perform an EXCHANGE command
between Slot 1 and Drive 2.  At time T0, two operations are
simu...