What happens when ARCH writers are writing the archive logs?

We have a database that runs three archiving processes. We have another process (Tivoli Storage Manager) to remove the achive files to tape; via a Unix script. Can you tell me what happens when the ARC writers are writing the archive logs and what would happen if I was to remove one of those files? I have noticed that the archive writers open and close the files each time they write, but what I do not know is how it is all kept in sync.

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The ARCH process will open a file for output when an online redo log file needs to be archived. This still applies if there are multiple ARCn processes. Once the online redo log has been copied, or archived, then the ARCH process closes that file. ARCH will not reopen the archived redo log again. It will only open the specific archived log file that is is *currently* archiving. The system knows which file is currently being archived by its log sequence number. Hopefully, you use a LOG_ARCHIVE_FORMAT with '%S' in it so that each archived redo log has the log sequence number in the filename. This way, each archived log is guaranteed to have a unique filename.

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This was first published in December 2002

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