Questions about ontape

What kind of backup is ontape? How does it work? Is it a "dd" or something else? I have read we can work through the backup with no ill-effects, but will processing be slowed? Are tables or other structures locked, other than blobs fields, when the archive is running? We want to run a mergeid process at night, when these ontape archives are being created. TIA and thanks for answering my earlier questions today! Cathy Geier Unix/web/DB admin Northwestern College St. Paul, MN 651-631-5284

CKGeier@nwc.edu wrote: > > What kind of backup is ontape? How does it work? Is it a "dd" or something Something else, read below. > else? I have read we can work through the backup with no ill-effects, but Correct. > will processing be slowed? Are tables or other structures locked, other Nothing is locked except BLOB pages temporarily (see the Backup and Restore Guide for details). > than blobs fields, when the archive is running? We want to run a mergeid > process at night, when these ontape archives are being created. No problem. > TIA and thanks for answering my earlier questions today! Ontape is Informix's original claim to fame. When Informix first developed its enterprise quality engine (it already had the Standard Engine) it was named Informix Online because you could safely archive it using ontape without having to kick users off and shutdown the engine as you had to at the time for virtually ALL other database servers and there was minimal impact on production. Truth is until IDS7.2x the impact was noticeable but the process has been constantly improved over the years. In IDS7.3x and IDS9.2x there is no noticeable impact on current performance during an archive. I have servers with over 400GB of disk chunks that take over 36 hours to archive to a 5 DLT7000 drive RAID tape array so I run archives during production almost every day (we alternate archiving each of two sister machines so I have a window for maintenance like adding chunks on the off days). Ontape accomplishes this feat by archiving directly from disk to tape through a private set of buffers that does not affect the system buffer cache. Informix maintains data integrity through concurrent updates by having the engine copy the preimage of any page modified after the start of the archive to a set of temp tables, one per dbspace. Once each dbspace has been copied to the archive device/file that dbspace's temp table is dumped to the archive device as well and (in 7.30 or later) dropped. Thus during a restore any page modified during the archive which may or may not have had its altered version flushed to disk before the archive got to it will be overwritten with the preimage copy and thus restored to its original condition as-of the start of the archive. Art S. Kagel