While the extended contingent allegiance condition exists, the target shall respond to any other request for access to the logical unit from another initiator with BUSY status. Execution of all I/O processes for the logical unit for which the extended contingent allegiance condition exists shall be suspended until the RELEASE RECOVERY message is received by the target.
( It is not required to generate an extended contingent allegiance condition for every CHECK CONDITION or COMMAND TERMINATED status that occurs. Simple errors not requiring an extended recovery may be dealt with by using the contingent allegiance protocol. ) ( During the existence of the extended contingent allegiance condition, appropriate error recovery sequences may be executed. Such commands can correct data, modify or delete queued commands, perform LOG SENSE commands and obtain diagnostic information. Extended contingent allegiance is recommended for error conditions that may require execution of multiple-step error-recovery protocols without interference from other initiators. )
An extended contingent allegiance condition may also be generated using an asynchronous event notification protocol. When the event is detected, the bus device that detected the event assumes the initiator role and transmits a SEND command with an AEN bit of one to the appropriate device(s) (see 12.2.2).
If the device wishes to generate an extended contingent allegiance condition during an asynchronous event notification, it shall send an INITIATE RECOVERY message following the IDENTIFY message (and following any queue tag message) and prior to the COMMAND phase of the SEND command. An extended contingent allegiance condition can be generated for only one I_T_L nexus at a time. The extended contingent allegiance condition is cleared when a RELEASE RECOVERY message is received from the device to which the INITIATE RECOVERY message was sent. The generation of a hard reset condition, or receipt of a BUS DEVICE RESET message, shall also clear the extended contingent allegiance condition.
During an extended contingent allegiance, only untagged I/O processes from the SCSI device to which the INITIATE RECOVERY message was sent shall be executed by the target for the logical unit. If the initiator sends a queue tag message, the target shall respond with QUEUE FULL status. After the extended contingent allegiance condition is cleared, any commands remaining in the command queue shall be executed.