5.34RESERVE (10) Command (56h)
The RESERVE and the RELEASE commands are used for contention resolution in
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Bit | 7 | 6 | 5 |
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0 |
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| Operation | Code (56h) |
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1 |
| Reserved |
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| 3rdPty |
| Reserved |
| LongID | Extent | |
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2 |
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| Reservation | Identification |
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3 |
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| Third Party Device ID |
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4 - 6 |
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7 - 8 | (MSB) |
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| Parameter List Length |
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9 |
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| Control |
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Field | Description | |
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3rd Pty | When set to 1, it indicates that the Third Party Device ID field is valid. | |
| When 0, indicates that the third party device associated with the reservation release has a number | |
LongID | smaller than 255 and the ID value can be sent within the CDB. If set = 1, indicates that the third | |
party device ID is greater than 255, the ID value within the CDB is ignored, and the parameter list | ||
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| length is at least eight. | |
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| Required and used only when the 3rdPty bit is set, in which case this field specifies the SCSI ID | |
| of the initiator to be granted the reservation of the logical unit. The drive preserves the reservation | |
| until one of the following occurs: | |
| • It is superseded by another valid RESERVE command from the initiator. | |
Third Party | • It is released by the same initiator. | |
• It is released by a TARGET RESET message from any initiator. | ||
Device ID | ||
• It is released by a hard reset condition. | ||
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| The drive ignores any attempt to release the reservation made by any other initiator. For example, | |
| if ID7 sends ID2 a Third Party reservation on behalf of ID6 (the target at ID2 gets reserved for the | |
| initiator ID6), then only ID7 can release the target at ID2 (using a Third Party release). ID6 cannot | |
| release the reservation even though the reservation was made on its behalf. | |
| If 0, requests that the entire logical unit be reserved for use only by the initiator until the request | |
| is supplanted by another valid RESERVE command from the same initiator, or until released via | |
| a RELEASE (10) command from the reserving initiator, a hard reset, or a power on cycle. | |
| If set = 1, the extent reservation option is implemented. This option allows an application client in | |
Extent | a multitasking environment to have multiple reservations. | |
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| The size of the extent list is defined by the contents of the Parameter List Length field. The extent | |
| list consists of zero or more descriptors. Each descriptor defines an extent beginning at the speci- | |
| fied logical block address for the specified number of blocks. If the number of blocks is 0, the ex- | |
| tent begins at the specified logical block address and continues through the last logical block | |
| address on the logical unit. The data format of extent descriptors is shown in Table |