2 ACSLS Logical Libraries

The ACSLS Logical Library (referred to in this document simply as “logical library") is a subset of one or more connected physical libraries (drives and volumes). It is currently presented over two interfaces: one is the SCSI and the other is the ACSLS Graphical User Interface (referred to in this document simply as “GUI"). This document covers the SCSI/FCP interface and mentions the GUI only where it has impact on the SCSI interface. For more information on the management of logical libraries, refer to the ACSLS documentation.

The ACSLS system (referred to in this document simply as the “system") presents each logical library as a SCSI Media Changer (SMC) device. Each device appears as a separate LUN on a Fibre Channel (FC) target port contained on the system. Initiator mode FCP SCSI applications (referred to in this document simply as hosts or host applications) attach to the system through a FC SAN and communicate with the logical library using the SCSI commands described in this document. Also attached to the system are one or more physical libraries. A physical library can be any type of library supported by the system. This may include both SCSI and non-SCSI (HLI) libraries. A logical library uses some or all of the resources of one or more physical libraries. A logical library cannot span more than one physical library unless the physical libraries are connected together with a pass through mechanism. The system presents each logical library as a single SCSI library on its own LUN even if the logical library has been configured to use resources from more than one physical library. The system provides LUN masking so that each host sees only the logical libraries that have been configured for it. Only one host connection per logical library is allowed. With this restriction, reservations and reservation conflicts are not possible and are therefore not described in this document.

A logical library is created by a System Administrator (referred to in this document simply as the “administrator") using the GUI. The resources of the library are mapped by the system to real resources of the associated physical library (s). This is described in more detail under Elements of a Logical Library below. From the perspective of the SCSI interface, a logical library behaves very much the same as a real SCSI Media Changer, but there are some differences. High level descriptions of these differences are described in this chapter. For detailed description of each command see SCSI Commands.