Re: Consistant database using archive 0 question

PLKapp (plkapp@aol.com) wrote: : --- 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. Yes, you can restore without logfiles. If the logfiles are not restored, all transactions that took place during the archive are ignored. All transactions that were in progress when the archive was taken will be rolled back after the archive is restored and the system brought back on-line. : >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. Before-images are written to the physical log, not a temporary table. Otherwise, this is essentially correct. The archive does not back-up any pages with a timestamp later than the checkpoint which was forced by the archive process. If you don't rollforward logs, the Fast Recovery process which OnLine always goes through when brought back on-line will roll back all open transactions from the last checkpoint (when the archive started). June ---- June Tong Informix Software ---- ---- Senior Consultant (415) 926-6140 ---- ---- International Support junet@informix.com ---- ---- Location-du-jour: Menlo Park ----