There have been issues seen with the (then current) methods of performing IO retry when SCSI Inquiry succeeds and IO to the device fails. This section of IO recovery has been significanlty changed as of the release of 5.1SP1.  New Tunables have been introduced to allow configuration of IO recovery options.  NOTE: These examples are NOT recommendations. They are simply usage examples. Settings for your environment may differ or need some tuning for your particular environment. 

#vxdmpadm getattr enclosure <enclr-name> dmp_lun_retry_timeout

 Note about the iotimeout value when the Timebound option is used:

This value should be high enough to allow the underlying SCSI driver to fail a path to a device before the iotimeout expires. If the iotimeout expires before the path is failed ( unresponsive device due to SAN fabic failure, etc.) alternate paths are not tried and the DMP node will be disabled. There are certain OS configurations where the SCSI driver will not fail a device for at least 300 seconds, so a value of more than 300 would be required to ensure the other paths are tried before the device is disabled. See TECH174945 for a specifc example of a Solaris configuration that has this issue. Note that Timebound[300] (300 second iotimeout value) is the default.