updates during ontape

Hi folks (a theoretical scenario) John the dba starts an Informix ontape level 0 at 11:00am At 11:20am a batch update utility starts. At 12:00pm the ontape level 0 finishes At 1:20pm the load finishes. The question is: Will the ontape backup contain 1. none 2. some or 3. all of the rows updated in the update job. Also, how does Informix decide where in the log a level 0 archive is taken, is it at the start or at the end? regards Justin Abbott Sent via Deja.com http://www.deja.com/ Share what you know. Learn what you don't.

In article <7liop9$fs4$1@nnrp1.deja.com>, Justin Abbott <abbotj@my-deja.com> wrote: > Hi folks > (a theoretical scenario) > > John the dba starts an Informix ontape level 0 at 11:00am > At 11:20am a batch update utility starts. > At 12:00pm the ontape level 0 finishes > At 1:20pm the load finishes. > > The question is: > Will the ontape backup contain > 1. none > 2. some or > 3. all of the rows updated in the update job. Choice 2. > > Also, how does Informix decide where in the log a level 0 archive is > taken, is it at the start or at the end? When Informix begins new archive, begin-archive timestamp is noticed. All dirty pages, being flushed during the archive process are also stored in the temp space, and also came into archive. The pages with timestamp higher then archive end-timestamp will not be stored by ontape. -- With best regards, Yuri Dovgart, SAP R/3, Informix consultant, "Telecominvest" company. E-mail y_dovgart@tci.ukrtel.net Sent via Deja.com http://www.deja.com/ Share what you know. Learn what you don't.

Justin Abbott wrote: > > Hi folks > (a theoretical scenario) > > John the dba starts an Informix ontape level 0 at 11:00am > At 11:20am a batch update utility starts. > At 12:00pm the ontape level 0 finishes > At 1:20pm the load finishes. > > The question is: > Will the ontape backup contain > 1. none > 2. some or > 3. all of the rows updated in the update job. None. Informix archives are point in time. All modifications to the server and tables and data within made during the archive are NOT included. This is done by copying the unchanged page pre-images from the physical log out to the tape. In versions 7.20+ this is done by having a thread constantly copy any physical log pages with a timestamp earlier than the start of the archive to temp tables, one per dbspace, and after each dbspace is completely archived the preimages from that dbspace's temp table are flushed out. During a restore these pages are what are restored for any pages modified during the archive. > Also, how does Informix decide where in the log a level 0 archive is > taken, is it at the start or at the end? The fact of the beginning of the archive is noted in the logical log for information sake but it is not used for anything. The current page timestamp, which is a number incremented each time a page is modified in the buffer cache, is noted as the beginning of the archive and any pages with an earlier timestamp on disk are copied (the archive starts with a checkpoint so any pages in memory can be ignored as either identical to disk of post archive mods. Art S. Kagel

Yuri Dovgart wrote in message <7lipbj$g4p$1@nnrp1.deja.com>... >In article <7liop9$fs4$1@nnrp1.deja.com>, > Justin Abbott <abbotj@my-deja.com> wrote: >> Hi folks >> (a theoretical scenario) >> >> John the dba starts an Informix ontape level 0 at 11:00am >> At 11:20am a batch update utility starts. >> At 12:00pm the ontape level 0 finishes >> At 1:20pm the load finishes. >> >> The question is: >> Will the ontape backup contain >> 1. none >> 2. some or >> 3. all of the rows updated in the update job. > >Choice 2. Strictly speaking this may be right, but I think the spirit of the question is "If I do a restore from this archive will I have the rows?", and the answer to THAT question is No. Neil Truby Londis Stores Hampton Hill, UK