Re: Moving txn log between machines
Scott Boake <scott@palan.uucp> writes - > I have an idea I wanted to bounce off of you good people. (Fetches can-opener, opens fresh supply of worms.) Scenario: (paraphrasing) * Informix upgrade, 2.1 to 4.1 with OnLine engine * S/ware 4GL/RDS * Platform 486/33 PC * Min. downtime requirement suggests use of second PC, kept in sync with first by copying txn log to second and rolling forward the DB on the second. How you do this depends a lot on whether you run the Standard Engine (C-ISAM, normal "cooked" unix files) or the OnLine engine proper (raw disk access, much faster, much better protection and recovery of data). > Is there a way with the 4.1 On-Line I can tell it to start a new transaction > log file without interuppting operations? With standard engine, yup: START DATABASE foobar WITH LOG IN "/usr/trans_log" Have something to loop around and give you fresh filenames each time. Whenever the old file's closed you should be ok to copy (rcp, ftp, etc) it to the second machine and do the rollforward. With OnLine engine proper: The logfiles ("logical logs") are written into raw disk space and the only easy way you can get to them is "archive" them, either to disk or to tape. Sounds like the way to do this is to run continuous archiving to a tape in PC #1 and, if PC #1 crashes, bung the tape of the logs in PC #2. The only way I can see of getting OnLine to rollforward from logical logs is to have just done a full restore, though. Any other way, guys ? Also, the roll-forward may take a non-trivial time, depending on your throughput. OnLine (NOT SE) *does* give disk mirroring, which would normally be used for a requirement like this. How are the disks connected to the PCs ? Is it, for example, possible to have them all on the PC #1, and mirrored - with the option to connect them all to PC #2 on failure of PC #1 ? In this case, failure of any half of each pair of disks would have no effect. > I heard some place recently that On-Line 4.1 recommends many small transaction > log files as opossed to a few large transaction files. This is for logs in raw filespace (and probably depends quite a lot on the type of work you're doing and throughput). > Any suggestions / comments are welcome! How big's the DB and transactions, and what rate of transactions are you doing ? Talk to Walt Hultgren (walt@rmy.emory.edu) about getting on the list, BTW ! > ---Scott > > Scott Boake Palantir Systems, Inc. > scott@palan 5030 - 78th Ave N Ste 11 > (813) 544-8152 Pinellas Park, FL 34665 How come you don't answer your 'phone ? 8^) All the best. -- Cheers - Tony. ____________________________________________________________________________ Tony Heskett: theskett@lhr-sys.ssf-sys.dhl.com | Vox: (+44) 81 747 8330 DHL Systems : Kings House, Great West Road, TW8 9HS | Fax: (+44) 81 747 0875