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OK, a bit more details... 1) With RAID you have protection against loss of one drive per parity set. If more than one drive fails, or controller card goes down, then you are out. Obviously, mirroring provides higher level of protection - unit, controller or bus level, depending on setup. But it comes at a greater cost - all hardware should be duplicated. So RAID and mirroring are two alternative protection strategies - you choose what better suits your environment. (RAID and mirroring can be mixed - you can have RAID-protected and mirrored units in the same ASP. This creates greater granularity for choosing best protection.) 4 and 5) I believe, entry sequence number in journal is upto 2 billion+ (4-byte signed integer). For system-managed journals system is supposed to do whatever maintenance is needed automatically. I am not sure whether it will be reset or will just wrap - I think it will be reset by system. Occasionally, QDBJRN needs manual attention - I remember a system with QDNJRNxxx journal receiver hitting 2GB limit. System freezed up and would not work until CHGJRN was done manually. But it was clearly not designed to be so and should not happen. 6) SMAPP is System-Managed Access Path Protection - system takes care of access path which were not explicitly journalled. You control SMAPP from EDTRCYAP display. This feature is described in Backup and recovery Guide. Hope this helps... Best regards Alexey Pytel Dave Mahadevan <mahadevan@fuse.net> on 04/27/99 11:34:12 AM Please respond to MIDRANGE-L@midrange.com To: midrangel <MIDRANGE-L@midrange.com> cc: (bcc: Alexei Pytel/Rochester/IBM) Subject: Re: Puzzling System Action Alexey: > 1) When you start mirroring on ASP, which contains RAIDed drives, system > will consider RAIDed drives already proctected and will leave them alone. > Only non-RAID protected drives will be paired. > In other words, if you have ASP containing only RAID-protected drives, > starting mirroring for them will not change anything. > If you really want mirrored protection, stop RAID-protection for drives in > ASP, and then start mirroring. > Ok I understand. Stupid question: How am I protected when the subsystem goes down? I switched off one of the subsystems. Jobs accessing libraries in the RAID freezes and the system reports a missing disk with A6xx0244. Interesting behaviour. I guess the protection is only on the unit level within the subsystem. Pardon my ignorance, why cant RAID systems be mirrored? > 4 and 5) QDBJRN (in QRECOVERY) is an internal system journal, which > protects system dictionary files (QADBxxx). System takes care of this > journal automatically, so normally user does not need to do anything about > it. If you want to reset sequence numbers, try to do it in a restricted > state. > Is resetting really necessary? How high can the sequence numbers go? > 6) When SMAPP is active (EDTRCYAP), system may write internal - invisible - > entries to journals. These entries record changes to not-journaled access > paths.These entries cannot be accessed by user, but they do consume > sequence numbers. > > You lost me here. Maybe a little more explanation or a manual reference? Thanks. > Best regards > Alexey Pytel > -- Thank You. Regards Dave Mahadevan.. mailto:mahadevan@fuse.net +--- | This is the Midrange System Mailing List! | To submit a new message, send your mail to MIDRANGE-L@midrange.com. | To subscribe to this list send email to MIDRANGE-L-SUB@midrange.com. | To unsubscribe from this list send email to MIDRANGE-L-UNSUB@midrange.com. | Questions should be directed to the list owner/operator: david@midrange.com +--- +--- | This is the Midrange System Mailing List! | To submit a new message, send your mail to MIDRANGE-L@midrange.com. | To subscribe to this list send email to MIDRANGE-L-SUB@midrange.com. | To unsubscribe from this list send email to MIDRANGE-L-UNSUB@midrange.com. | Questions should be directed to the list owner/operator: david@midrange.com +---
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