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4-38 IBM Informix OnLine Database Server Administrator’s Guide
Archive Disk Pages That Meet Criteria
A level-1 archive directs tbtape to consider a narrower range of used pages.
The archive criteria become all disk pages containing a timestamp that is less
than the begin-archive checkpoint timestamp but greater than the timestamp
associated with the most recent level-0 archive. The tbtape process reads the
value of the most-recent level-0 archive timestamp from the active
PAGE_ARCH reserved page.
A level-2 archive also directs tbtape to consider a narrower range of used
pages. The archive criteria become all disk pages containing a timestamp that
is less than the begin-archive checkpoint timestamp but greater than the
timestamp associated with the most recent archive (any other level). Again,
tbtape reads the value of the most-recent archive timestamp from the active
PAGE_ARCH reserved page.
Archive Disk Pages That Meet Criteria
After the archive criteria are established, tbtape begins to read the disk pages
in the chunk that is identified with chunk number 1. Each of the chunks is
read in order. (OnLine chunks are listed in order in the active PAGE_PCHUNK
reserved page.) Each page that meets the tbtape criteria for archiving is
copied to the archive tape.
Monitor and Archive Physical Log Pages
While tbtape reads disk pages, it periodically reads the pages stored in the
physical log, looking for pages that meet the archive timestamp criterion.
Each page that qualifies is copied to the archive tape. (Refer to page 4-34.)
Write a Trailer Page
When tbtape reaches the last page of the last chunk, the disk-reading portion
of the archive procedure is complete. The tbtape process writes a trailer page
to the tape, marking the end of the archive tape.
Update the Reserved Pages
As the last step in the archive process, tbtape updates the active PAGE_ARCH
reserved page with the newest archive information.