RE: on bar procedure

Hi, only so-called "whole system backups" (done with "onbar -b -w ...") can be restored to a consistent system without logical log restore. Please read the "Backup and Restore Guide" manual for more information on the requirements and consequences of this. Normal ON-Bar backups (done without "-w") ALWAYS need logical logs for the restore in order to restore to a consistent system. This is even the case when you do not want to roll forward logical logs to reach a point in time after the physical dbspace backup. This also means that keeping a normal level-0 backup, e.g. in "long-time storage", but not keeping the logical log file backups will not be helpful, because you will not be able to restore properly from that level-0 backup alone (without those logical logs). For such things, whole system backups shoul be done. [ Normal physical dbspace backups (i.e. without "-w") do not backup any logical log records, because it is assumed (and documented) that logical logs have to be backed up separately. Since the physical backup of dbspaces (generally) is done in parallel, each dbspace has its own archive checkpoint. This means the dbspace backups are consistent by themselves, but not relative to each other. These inconsistencies between the different dbspace backups are then resolved during restore by applying logical log records to "bring them all to consistency at the same point in time". Therefore logical log files "from around the time of the physical dbspace backup" are necessary for restore. Apart from that, logical log records may also be necessary to roll back transactions that were open at the time of the physical dbspace backup. This may involve log records from logical log files that were backed up quite some time before the physiacl dbspace backup was done (depending on how far open transactions go back). Therefore logical log files "from way before the time of physical dbspace backup" may be necessary for restore. Whole system backups do not need logical log file restore, because all dbspaces are backed up with the same checkpoint, so there is no inconsistency between different dbspace backups. And the whole system backup will contain all log records of transactions that are open at physical dbspace backup time. So these transactions can be rolled back during restore, even when no logical logs are restored. Therefore whole system backup is the only backup that can be properly restored without logical log file restore. ] Unfortunately it is not straightforward (though still possible) to figure out which particular logical log files are needed as a minimum for restoring a particular normal dbspace backup. Therefore the general rule usually is to better safe-keep them all. (The onsmsync utility does check for these things correctly, drawing on internal information from the sysutils database.) Regards, Martin -- Martin Fuerderer IBM Informix Development Munich, Germany Information Management owner-informix-list@iiug.org wrote on 03.05.2005 23:08:42: > > In addition to what others have said, you may need your "emergency boot" > file so onbar knows what volumes to ask from the volume manager. Hence your > unix (assumption) backup should be after your informix archive. > > I presume whatever storage manager you use is retrievable or on a different > server. > > MW > >> owner-informix-list@iiug.org wrote on 03.05.2005 19:59:54: >> >> Additionally, if by any chance you find that the latest level 0 is >> unreadable you might need to go back more than 24 hours. So make sure >> that your log backup is getting backed up by OS backup as well, >> especially if you allow idiots to do sysadmin functions. >> >> Regards >> >> Malcolm >> >>> -----Original Message----- >>> From: owner-informix-list@iiug.org [mailto:owner-informix-list@iiug.org] >>> On Behalf Of Simmons, Keith >>> Sent: 03 May 2005 16:19 >>> To: coleas@gmail.com; informix-list@iiug.org >>> Subject: RE: on bar procedure >>> >>> >>> Yes, but you will not be able to roll forward you logs to reach the >>> point of failure, therefore you risk losing up to 24 hours worth of >>> processing. All well and good if you can afford this, however if not >>> either make the directory and its contents bullet proof, or backup the >>> logs to tape. >>> >>> Keith >>> >>> > -----Original Message----- >>> > From: owner-informix-list@iiug.org >>> > [mailto:owner-informix-list@iiug.org] On Behalf Of coleas@gmail.com >>> > Sent: Tuesday, 3 May 2005 2:52 p.m. >>> > To: informix-list@iiug.org >>> > Subject: on bar procedure >>> > >>> > Hi all >>> > >>> > Just a quick question. >>> > My on bar procedure is to backup logs to the hardrive and do >>> > a level 0 to tape at night. >>> > If I loose the harddrive log backup (some idiot deletes the >>> > directory) can I still restore from the level 0. >>> > >>> > thanks >>> > >>> sending to informix-list sending to informix-list