
System Architecture 2-93
OnLine Limits for Chunks
If the primary chunk goes down and the mirror chunk becomes the primary
chunk, disk space allocation reports will accurately describe the fullness of
the new primary chunk.
Figure 2-16illustratesthemirrorchunkstructureasitappearsafterthechunk
is created.
OnLine Limits for Chunks
The maximum number of chunks that can exist within an OnLine configu-
ration might be operating-system dependent. The maximum value is the
lesser of the following two values:
■ Thenumberofchunkentries (pathnames)thatcanfitonapage.(Use
tbcheck -pr to display chunk pathnames. Refer to page 2-100.)
■ The maximum number of files a user process can hold open, minus
6. (The maximum number is defined by the operating system.)
OnLineallocatesonepageformaintainingitslistofchunks.OnLineinstalled
on a machine with a 4-KB page size can accommodate twice as many equal-
sized chunk entries as canan OnLinedatabase serverinstalled on a machine
with a 2-KB page.
Figure 2-16
Structures within a
mirror chunk after
the chunk is
created
Number and type of control pages varies,
depending on chunk type.
Generic mirror
chunk
Remaining spacein amirror
chunk is marked as full.
Control pages
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