
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.
Thearchivecriteriabecomeall disk pagescontainingatimestampthat is less
thanthebegin-archivecheckpointtimestampbutgreaterthanthetimestamp
associated withthe mostrecent level-0 archive. Thetbtape process readsthe
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.Thearchivecriteriabecomealldiskpagescontainingatimestampthat
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
Afterthearchivecriteria areestablished,tbtapebeginstoreadthediskpages
in the chunk that is identified with chunk number 1. Each of the chunks is
readinorder.(OnLinechunksarelistedinorderintheactivePAGE_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
Whentbtape reachesthelastpageofthelastchunk,thedisk-readingportion
ofthearchiveprocedureiscomplete.The tbtape processwritesa trailer page
to the tape, marking the end of the archive tape.
Update the Reserved Pages
Asthelast step in the archiveprocess,tbtapeupdatestheactivePAGE_ARCH
reserved page with the newest archive information.
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