For the initial bulk load on a newly installed frame, insert cartridges into the deep slots, but  leave the top two rows empty. The slots in the top two rows must be empty for the initial audit  of the frame to start, and to enable the initial shuffle operation to proceed. The initial audit fills  these slots, and then these slots are used like any other HD slot in subsequent library  operations. First-generation HD (HD1) frames can be installed to the right side of an Lx5 frame only. Second-generation HD (HD2) frames provide the following enhancements: The position and configuration of the frame and the installation of CoD features affect the total  available storage capacity of the S25 and S55 frames. Table 1-7 lists the available storage  capacity based on possible frame positions and configurations. The TS4500 High Availability (HA) option provides a second accessor for redundancy and  performance. This feature allows dual accessors in a dual active mode, and it features an  integrated service bay to reduce service space. The integrated service bays replace the existing HA frame and Service Bay B frames that are  used on the TS3500. The integrated service bays allows a section of a frame to be used for  servicing an accessor while the remaining portion of the frame is still available for active  storage and drives. Accessor service must be performed through the side, by opening the  side doors of integrated service bays. Any HD2 frame can be an integrated service bay.  Chapter 1. IBM TS4500 tape library  19 1.2.4 TS4500 High Availability (HA) option GLYPH<SM590000> They can be installed in the leftmost library position (frame position 1). GLYPH<SM590000> They offer drive-capable models that support up to 16 HD2-compatible tape drives when  in frame position 2 or higher. Table 1-7 Quantity of storage slots in S25/S55 frame Model Licensed features  Frame  position Quantity  of drives Quantity  of T0  slots Quantity of  T1 - 4/ 5 slots  per tier Quantity of  licensed slots  available for use S25 S25 Base Any 1 - 12 160 160 0,600 S55 S55 Base Any 1 - 12 176 176 0,660 S25 S25 HD  CoD 1 0 - 12 160 160 0,798 S55 S55 HD  CoD 1 0 - 16 176 176 1,054 S25 S25 HD  CoD 2+ 0 - 12 2000 200 1,000 S55 S55 HD  CoD 2+ 0 - 16 220 220 1,320 S24 S24 HD  CoD 2+ 0 - 12 200 200 1,000 S54 S54 HD  CoD 2+ 0 - 16 220 220 1,320