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Illegal SCSI bus phase detected on bus

Nasimuddin Ansari_1
Occasional Advisor

Illegal SCSI bus phase detected on bus

Hi All,
In one of tru64 server belopw messases are being logged repeatedlt in 2-3 minutes interval in /var/adm/messages. Please suggest where the problem is ..

10:15:05 server01 vmunix: scsi11: Unable to stop SCRIPTS processor on bus 11
10:15:05 server01 vmunix: scsi11: SCSI Bus was reset
10:15:05 server01 vmunix: scsi11: Illegal SCSI bus phase detected on bus 11, resetting bus
10:15:05 server01 vmunix: scsi11: SCSI Bus was reset
10:18:39 server01 vmunix: scsi11: HTH intr. on bus 11, SBCL = 0x0
10:18:39 server01 vmunix: scsi11: SCSI Bus was reset

TIA
3 REPLIES
Vladimir Fabecic
Honored Contributor

Re: Illegal SCSI bus phase detected on bus

It is hard to say what is the problem, expecially without lots of details.
It may be hardware problem, so errorlog may help.
What kind of alpha server you have and what is your OS version?
When problem started?
And first send output of:
# scu show edt
and
# hwmgr -show scsi (if you have 5.X)
In vino veritas, in VMS cluster
DCBrown
Frequent Advisor

Re: Illegal SCSI bus phase detected on bus

This means that there was a scsi bus phase issue. That is, the bus transaction didn't follow the expected protocol. Typical bus hardware transaction might be arb/select/ident followed by message out phase, etc. Something like:

Arb Start
Arb Win
Sel Start
Sel End
Msg Out
Command Write 0Ah
Msg In Save Data Pointer
Msg In Disconnect
Bus Free

If a Bus Free phase was detected instead of message-in phase when it was expected, for example, then that would be an illegal bus phase and cause the reset. Without a scsi bus trace you won't know exactly what the cause is, but it is likely either a noisy bus (any cables touched recently) or a bad device. I picked on Bus Free phase because that is typical/common. Something happens, like bus parity error detected, and the initiator controlling the bus drops the bus into Bus Free phase to terminate the transaction.


Nasimuddin Ansari_1
Occasional Advisor

Re: Illegal SCSI bus phase detected on bus

We found from scu show edt that on bus 11, SCSI tape drive was connected and creating problem. Once removed from the server, message disappered.

Thanks to all.