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2-150 IBM Informix OnLine Database Server Administrator’s Guide
Structure of a Blobspace Blobpage
Figure 2-38 illustrates the structure of a blobpage.
The blobpage header includes the following information:
■ The physical address of the blobpage
■ A page-header timestamp that indicates the last time this blobpage
was modified
■ A forward pointer to the blobpage that holds the next segment of
blob data and an associated blob timestamp, if a next segment exists;
otherwise, only the current page number appears, indicating this is
the last page
■ A blob timestamp that describes the last time this page was allocated
(when blob data was written to the page)
■ The size of this blobpage
■ A percentage of blobpage fullness
■ A unique identifier that is written when a blobpage is written to tape
(used only during the data restore procedure)
Figure 2-38
General
structure of a
blobpage. The size
of a blobpage must
be a multiple of the
page size.
Blob data segment
Page header
Free space
Timestamp
Blobpage structure