In addition to performance scaling, performance segmentation is a function that allows you to divide the tape into longitudinal segments. Using this optional data class specification, it is possible to segment the tape into two segments: one as a fast access segment to be filled first, and the other as additional capacity to be filled after the first segment is filled.
The 3592 Model J tape subsystem supports the performance segmentation option on the IBM Enterprise Tape Cartridge (MEDIA5). The 3592-2 and 3592-2E, 3592-2E, and 3592-3E models support the performance segmentation option on the IBM Enterprise Tape Cartridge (MEDIA5) and the IBM Enterprise Extended Tape Cartridge (MEDIA9). The 3592-4E model supports the performance segmentation option on the IBM Enterprise Extended Tape Cartridge (MEDIA9) and on the IBM Enterprise Advanced Tape Cartridge (MEDIA11). Where applicable, both the encryption and the non-encryption formats are supported. When using the performance segmentation option, the overall capacity of the cartridge is limited to 86.6% of the total capacity. The fast access segment occupies the first 20% of the cartridge, followed by the slower access segment. So, for example, using EFMT2 or EEFMT2, a MEDIA5 cartridge written on a 3592 Model E05 has a capacity of 500 GB. If the cartridge is performance segmented, the MEDIA5 cartridge is segmented into a 100 GB fast access segment and a 333 GB slower access segment (for a total capacity of 433 GB). By default, the MEDIA5, MEDIA9, or MEDIA11 cartridge is used to its full capacity. When written from loadpoint, the segmented tape cartridge is reformatted according to the assigned data class.
Because a segmented cartridge only has one physical partition and one EOV indicator, data can only be written to the slower access segment after the fast access segment has been filled. If an application wants to manage what data is placed in which segment, the application needs to manually track and fill the fast access segment before it can place less frequently accessed data in the slower access segment.