to the TS3500 service bays. The default Maximum Capacity setting of the Elastic
Capacity feature eliminates the remaining unusable service space.
If the library is installed with the optional second accessor, cartridge mount
performance is also optimized. (A "mount" occurs when the accessor removes a
cartridge from a drive, returns it to its storage slot, collects another cartridge from
a random storage slot, moves it, and loads it into the drive.) The second accessor is
part of feature code 1442.
When dual accessors are installed and an attached host issues a command for
cartridge movement, the library automatically determines which accessor to mount
cartridge in the most timely manner. Depending on the settings, if the library's
primary accessor fails, the second accessor assumes control and eliminates system
outage or the need for operator immediate intervention.
If you already have an installed TS4500 tape library and you want to add a second
accessor, your IBM service representative can add the accessor. Converting from a
single accessor to a dual accessor disrupts the operations of the library.
The second accessor ships inside a Dx5 or Sx5 frame. You can place that frame
anywhere in the library string. However, the B accessor is always installed as the
right-most accessor.
Dual Accessor Settings
You have three options to choose from. Each option changes the zones within
which each accessor operates.
Dual active
Both accessors are online and active, and fulfill requests for media cartridges that
fall within each accessors preferred zone. In this option, the library is divided into
two equally sized zones. While both accessors are active, the A accessor services
the left zone and the B accessor services the right.
Accessor A Only
Only the A accessor is active and fulfills requests for media. The B accessor is
online but parked in Service Bay-B. If the A accessor goes down, then the B
accessor becomes active. In this option, the preferred zone for the A accessor
includes the entire library with the exception the area for Service Bay-B.
Accessor B Only
Only the B accessor is active and fulfills requests for media. The A accessor is
online but parked in Service Bay-A. If the B accessor goes down, then the A
accessor becomes active. In this option, the preferred zone for the B accessor
includes the entire library with the exception the area for Service Bay-A.
Service Bays
Accessors are serviced through the side doors at the ends of the library. All front
doors to remain closed during accessor service and eliminating the need for
dedicated service bay frames.
10 IBM TS4500: Introduction and Planning Guide
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