IBM System Storage TS3500, Introduction And Planning Manual

Page: 31 / 290

Dual accessors and service bays
This topic describes dual accessors and service bays and how they can enhance
library performance.
When an optional second accessor is installed, the TS3500 Tape Library features
enhanced availability by utilizing an additional accessor. The additional accessor
enables the library to operate without disruption if any component of the working
accessor fails.
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 1440 (Service Bay B Configuration), which can be ordered with
expansion frames used as service bay B. If you order a second accessor you must
also order a 3584 high availability (HA1) frame, which is also known as service
bay A.
As you view the library from the front, service bay A (the HA1 frame) is on the far
left and service bay B is on the far right. Figure 4 shows the location of service
bays in the TS3500 Tape Library.
When dual accessors are installed and an attached host issues a command for
cartridge movement, the library automatically determines which accessor can
r8a00005
Figure 4. Location of service bays in the TS3500 Tape Library
Chapter 1. Introduction
7