Re: Tape Support for Informix & Backups

On 2 Oct 98, at 19:29, riedyw@my-dejanews.com wrote: > Perhaps you could give me a hand. I am investigating alternative methods for > backing up and restoring our large Informix database. I have investigated > some of the alternatives and here is my summary. You missed OnBar. You don't mention which version of product you are using, but I assume it's OnLine. If you upgrade to (I think) 7.23 or greater, you will find OnBar, which works with all sorts of fancy backup devices, provided you have Legato, ADSM or OmniBack. It also offers more flexibility in what you have to back up. > 3) Currently our largest database is NOT running in log mode. If we were to > implement SQL data replication here at First Albany what is the recommended > logging method? Altering a database from non-logged to logged mode can be > done in several ways (ontape being one of them). What is the implication of > this action? Does it require additional disk space for data? What should > the sizes of the logical/physical logs be? Is there a formula that you can > point me to, to determine this? The biggest implication will be the likely performance hit. Also, you could be spending a lot more time backing up logical logs. Since you are not currently logging at all, I suspect you should try buffered logging (no flames, please! :-) Buffered logging will minimise the performance hit, however, you are exposed to the risk of losing the committed transactions in your log buffer if the system crashes. If you want to minimise that risk, use unbuffered logging (which implies a _big_ performance hit). Sizing of your logical logs is a bit of an art form, but here's Billy's Crude Method(tm): take the biggest possible transaction in your system (such as individually updating each record in your largest table: no_of_records * rowsize) * maximum number of users (assuming they all run said transaction simultaneously) * 2. I seem to remember a better version in one of the courses, but I'm not sure. Also you need to split that up over a number of logs. This is also a bit of an art, but I try to get a medium number of logs of medium size, rather that 3 huge logs or 32000 small ones. The real art form is sizing your physical log and your physical and logical log buffers. This has major implications for performance. It is also covered in detail in the IDS Server admin course and the Administrator's Guide, which I don't feel like copy typing here.... :-) HTH. -- Ciao, Billy /Group Managing Director, The West Solutions Group: http://www.west.co.za \\ Drivel @ http://www.west.co.za/tasteless/ / \\ "Granted, Mr Wheeler's ideas are stupid and unreasonable, but he does own the company and I / think we should go along with him..." \\________________________________________________________________________________________________