Mode Select (6) - X'15'

The Mode Select (6) command is supported by the tape library. Table 1 shows the command format.
Note: In the future, the length of the mode parameter list for Mode Sense Page Code X'3F' (return all pages) might exceed 255 bytes. Then, use of the Mode Select (10) and Mode Sense (10) commands is to transfer all mode pages with one command. For this reason, use of the Mode Select (6) and Mode Sense (6) commands is not recommended.
Table 1. Mode Select (6) Command
Byte Bit 7


Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0


0 Operation Code (X'15')
1 LUN (Obsolete) PF (B'1') Reserved SP (B'0')
2 Reserved
3 Reserved
4 Parameter List Length
5 Vendor Specific (B'00') Reserved (B'0000') Flag (B'0') Link (B'0')
The following 3584 Tape Library-specific parameters apply:
  • PF: Page format. The PF bit is explicitly not checked.
  • Parameter List Length: Specifies the length (in bytes) of the mode parameter list that is transferred from the initiator to the target. A parameter list length of 0 indicates that no data is transferred. This condition is not considered an error. The target terminates the command with CHECK CONDITION status with associated sense data of 5/1A00 (Illegal Request, Parameter List Length Error) if the parameter list length results in the truncation of the mode parameter header, the mode parameter block descriptor, or any mode page.
Note: You can issue a Mode Sense for current values before a Mode Select to avoid accidentally attempting to set fields that cannot be changed by the initiator.
The following mode pages are supported by the tape library. For more detail, go to each "Related Reference."
  • Mode Page X'18': Fibre Channel Logical Unit Control Page (Fibre Channel control paths only)
  • Mode Page X'1C': Informational Exceptions Control
  • Mode Page X'1D': Element Address Assignment
  • Mode Page X'1E': Transport Geometry Parameters
  • Mode Page X'1F': Device Capabilities
  • Mode Page X'20': VU Mode Parameters Page