4.3 SCSI Commands
4.3.7 RESERVE command
Table 4.39 RESERVE command
Bit | 7 | 6 | 5 |
| 4 |
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| 2 | 1 | 0 |
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0 |
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1 |
| LUN |
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| Reserved |
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| Reserved |
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As with the RELEASE command (explained next), the RESERVE command controls exclusive access to the logical unit (ODD) in a
Any values specified for CDB bytes 1 to 5 are ignored. However, INIT should specify 00h for these bytes.
The RESERVE command reserves the entire ODD (logical unit) for a specific SCSI device. The ODD reserved by this command remains reserved until one of the following conditions is met:
•The RELEASE command is issued by the INIT that issued the RESERVE command.
•A BUS DEVICE RESET message is issued by an INIT.
•A RESET condition occurs.
•The ODD power is turned off and on again.
While an ODD is reserved for a SCSI device, an INIT having no "reservation authority" for the ODD might issue this command. If so, the command ends with RESERVATION CONFLICT status.
After ODD reservation is established, any commands, other than the INQUIRY, REQUEST SENSE, and RELEASE commands, issued by an INIT other than the SCSI device that reserved the ODD are rejected. The RESERVATION CONFLICT status is reported to the INIT that issued the command. The INQUIRY and REQUEST SENSE commands are executed normally even while the ODD is reserved for another SCSI device. The RELEASE command ends with GOOD status, but any RELEASE command issued by a SCSI device having no reservation authority for the applicable ODD is ignored.
