Move Medium - X'A5'

Edit online

Table 1 shows the format of the Move Medium command.

Table 1. Move Medium Command
Byte Bit 7
MSB		 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
LSB
0 Operation code (X'A5')
1 LUN (Obsolete) Reserved
2 Transport Element Address
3
4 Source Address
5
6 Destination Address
7
8 Reserved
9 Reserved
10 Reserved Invert (B'0')
11 HD control Reserved (B'0000') Flag (B'0') Link (B'0')
  • Transport Element Address: For any of these values, the library selects an MTE based on optimal availability and performance. The following values apply:
      X'0000'  
      X'0001'  
      X'0002'
  • Source/Destination Addresses: The valid element addresses for these fields depend on the library's configuration. (See SCSI element addresses.)
    Notes:
    1. The Medium Transport Element is not capable of storing a media element. If this element address is specified as a Destination Address in a Move Medium command, the command is presented CHECK CONDITION status with associated sense data of 5/2101 (Illegal Request, Invalid Element Address).
    2. For the TS4500, if a destination element is an Ultrium 1 Tape Drive and the source element address contains an Ultrium 2 cartridge (VolTag of xxxxxxL2), the command is presented CHECK CONDITION status with associated sense data of 5/3000 (Illegal Request, Incompatible Medium Installed).
    3. For the TS4500, if a destination element is an Ultrium 1 or Ultrium 2 Tape Drive and the source element address contains an Ultrium 3 cartridge (VolTag of xxxxxxL3), the command is presented CHECK CONDITION status with associated sense data of 5/3000 (Illegal Request, Incompatible Medium Installed).
    4. If the source element address contains a cartridge that is assigned to another logical library (for example, exported to the shared I/O station or inserted into a shared tape drive), the command is presented CHECK CONDITION status with associated sense data of 5/3B81 (Illegal Request, Element Not Accessible, Cartridge is Assigned to Another Logical Library).
  • HD Control: The following values apply:
    B'00' Default behavior (Cache optimized)
    B'01' Tier 0 bypass (When the Source Move Element is a drive); Tier 0 destage (When the Source Move Element is a Tier 0 storage slot); Ignored for all other element types
    B'10' No unshuffle (Does not unshuffle cartridges that are shuffled out of an HD slot when the Source Move Element is from a Tier 3, 4, or 5 location)
    B'11' Optimized empty/fill sequence. (When the Source Move Element is a drive, the preferred destination is an empty HD slot. Once selected, that HD slot is then selected as the destination in successive usages of this option until the once-empty HD slot is full. Usage of this option requires frame/column/row/tier awareness for cartridges being moved to drives in order to create the empty HD slots.)
     
    Note:

    The depth of a cartridge location in an HD slot is known as a tier. The cartridge immediately accessible in an HD slot is a Tier 1 cartridge. Behind that is Tier 2, and so on. The maximum tier in an LTO HD slot is Tier 5. The maximum tier in a 3592 HD slot is Tier 4. The single-deep slots on the door-side of HD frames and in non-HD frames are referred to as Tier 0 slots.

    A shuffle operation is required to access any cartridge in Tier 2 or beyond. A shuffle is the process of moving cartridges in lower tiers into the gripper or other available slots to access cartridges in higher tiers. Tier 2 cartridges require a swap only by using the dual grippers (assuming both grippers are usable).

    To reduce the occurrence of shuffle operations and to take advantage of the typical repeated accesses of cartridges, the role of a cartridge cache is given to all single-deep (Tier 0) slots in an HD library. ALMS is required for libraries with HD frames so that cartridge placement is automatically optimized. However, the library supports some manual cache management operations by using the Move Medium HD Control bits.

    The HD Control bits allow an application to bypass cache on demount (drive-to-storage move, HD = B'01'), destage from cache to Tier 1 (storage-to-storage move, HD = B'01'), or to prestage a cartridge to cache from Tiers 3-5 (storage-to-storage move, HD = B'00'). With ALMS enabled, storage-to-storage moves previously resulted in no physical motion. The library now conditionally moves the cartridge between Tier 0 and HD slots for these cache operations.

    Drive-to-storage or storage-to-storage moves have the same effect as updating the cartridge "usage" date and time for consideration in subsequent LRU (Least Recently Used) cache destage operations. Hence, an application does not need awareness of the physical locations of cartridges to prepare a set of cartridges for faster future access. The application needs to send storage-to-storage moves only for the entire set of cartridges. If the cartridges are currently in Tier 0, they are protected from LRU destage. Also, they are protected if they are moved to cache (if currently in Tiers 3-5), or left alone (if currently in Tiers 1-2).

For additional information on element addresses and descriptions, refer to the following sections: