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4-32 IBM Informix OnLine Database Server Administrator’s Guide
Verify the Archive Level
Verify the Archive Level
As part of the archive request, you specify an archive level. The tbtape
process compares the specified archive level with the information that was
obtained from the PAGE_ARCH reserved page.
If tbtape cannot find a recordof a previous archive on thereserved page, the
only valid archive level is a level-0 archive. Otherwise, any archive level is
valid.
(Alevel-0 archive to /dev/nullregisters as avalidarchive.Therefore,OnLine
permits you to create a level-1 archive on a tape device if your only level-0
archive was created when the archive device was /dev/null. Because of the
problemsthiscouldcreateifadatarestorewereneeded,avoidthissituation.)
Check Free Space in the Logical Log
The tbtape process temporarily freezes the status of unreleased logical log
files and does not permit any log file to become free. The tbtape process
checks thetotal amount of free log space. Iffree space isless than half ofone
log file, OnLine refuses the archive request and recommends that you back
up the logical logs.
Force a Checkpoint
After tbtape verifies that the archive can proceed, it forces a checkpoint.
During thecheckpoint, tbtape gathers reference information that serves as a
snapshot of all OnLine data at this time.
The checkpoint marks the beginning of the archive. OnLine shared memory
and disk pages are brought to a consistent state. (Refer to page 2-70 for
further information about checkpoints.)
The address of the most-recently written record inthe current logicallog file
is noted.This recordbecomes the last record from thelog that will be copied
as part of this OnLine archive.
Ifthisarchiveisanonlinearchive,allchangestoOnLinedatathatoccurafter
this point are consideredbeyond therange of the archiveand are retained as
part of the logical log file records.
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