Re: Consistant database using archive 0 question

--- johnyc@mainelink.net Wrote on Sat, 06 Jan 96 03:38:30 GMT --- >Issue: Informix provides the capability to do a complete archive if a >database while it is in use. > >Question: Can this database be restored without any logfiles (ie to a test >environment) such that the database is consistant. That is, all transactions >that took place during the archive resulted in the archive either ignoring the >transaction completely or resolving the transaction by re-archiving pages that >were already archived and later made dirty during the cource of the archive. > >Example: An archive has archived the pages that contain rows 1 to 100 of a >savings account file. Money is transferred from the account in row 200 to the >account in row 10. What happens during the archive?? Is the data in row 200 >left untouched, or does the archive go back and get row 10?? It is my understanding that an archive contains an image of all data pages consistent with the assocaited forced checkpoint made at the start of the archive. The online engine is "aware" that an archive is in progress, and will save the pre-image of a page to a temporary table. When the archive progresses to that update page, it writes the old (checkpoint consistent) page data from the temp table. In your example, the update to row 200 will cause the old page image to be saved, the update will take place, and the archive will write data from the saved image. If you want to perform a fully up-to-date version onto another server, you could restore the archive, and roll forward the logs, which would re-play the updates to both row 200 and row 10, since the archive also forces the logical logs to advance at the forced checkpoint. Check the Online Archive and Backup Guide for a more thorough description of all the steps that go on during an archive. Paul Kapp ----> PLKapp@aol.com -OR- plk@interactive.visa.com