IBM AS/400e, Руководство пользователя

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Removable Storage Media Devices
366
AS/400e System Handbook
The cartridges on the 3494 must have human- and machine-readable external labels. These
are read by the accessor, which travels on a linear rail (extended when additional units are
added). The accessor uses a barcode reader. Its movement is horizontal, vertical, and 180
degree pivot.
Other optional features of the 3494 Tape Library Dataserver include a second Library
Manager Disk Drive (#5214), which allows mirroring of the Library Manager (basically a PC)
database. It also provides the capability to recover the Library Manager database in the event
of a failure on the primary disk drive. The Dual Gripper option (#5215) provides the accessor
with a second tape cartridge gripper for better performance in the Library.
IBM Magstar MP 3570 Tape Cassette Subsystem
The 3570 Tape Subsystem is based on the same technology as the IBM 3590 High
Performance Tape Subsystem. It functionally expands the capability of tape to perform both
write and read-intensive operations. It provides a faster data access than other tape
technologies with a drive time to read/write data of eight seconds from cassette insertion. The
3570 also incorporates a high-speed search function.
The 3570 uses a unique, robust, heavy usage tape cassette that is approximately half the
size of the IBM 3490/3590 cartridge tapes. The tape cassette capacity is 5G uncompressed
and up to 15G per cassette with LZ1 data compaction. The tape drive reads and writes data
in a 128-track format, reading and writing four tracks at a time. Data is written using an
interleaved serpentine longitudinal recording format starting at the center of the tape
(mid-tape load point) and continuing to near the end of the tape. The head is indexed to the
next set of four tracks and data is written back to the mid-tape load point. This process
continues in the other direction until the tape is full.
This tape cassette provides fast access to data by having two tape spools with the load point
in the middle of the tape. It is made from advanced metal particle media with servo tracks to