HP Surestore 28/48-Slot with DLT7000 Digital Linear Tape SCSI-2 Drive and SCSI - Page 41

NOTE SCSI Command Overview Library Control Commands Two queued Unit Attentions are not unusual. For example, if a library is powered up and a cartridge is loaded, Power Up and Not-Ready to Ready Transition Unit attentions are created. If an initiator does not clear Unit Attentions queued for it because of limited buffers, the tape device will eventually stop generating new Unit Attentions for the I-L combination (but existing ones will remain in queue). Not Ready Condition In contrast to the BUSY status condition, the Library Not Ready Sense Key is returned as part of the sense data following a Request Sense Command. This message indicates that a Media Access Command has been issued, and the media is not ready to be accessed. In the Not Ready state, the initiator cannot perform any operation that would cause library motion (move, exchange, position, etc.) or ask for data that is unknown (Mode Sense, Read Buffer, Write Buffer). These commands would return a CHECK CONDITION status with a Library Not Ready sense key. However, the initiator can execute commands that do not require access to the media, returning a GOOD status. The commands are as follows: • Inquiry • Log Sense/Select • Mode Sense/Select • Prevent/Allow Medium Removal • Read Element Status with curdata set • Receive Diagnostics Results • Request Sense • Reserve/Release Unit • Send Diagnostic (non-media or motion-access diagnostics) • Write Buffer • Report LUNS • Persistent Reserve In • Persistent Reserve Out Chapter 1 1- 17