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2-106 IBM Informix OnLine Database Server Administrator’s Guide
tblspace Tblspace
The hexadecimal representation of partnum is actually a composite of two
numbers. The most-significant 8 bits indicate the dbspace number where the
tblspace resides. The least-significant 24 bits indicate the logical page number
where the tblspace is described. Figure 2-19 on page 2-106 illustrates the
elements of a tblspace number.
Logical page numbers are relative to the tblspace. That is, the first page in a
tblspace is logical page 0. (Physical page numbers refer to the address of the
page in the chunk.) For example, the tblspace number of the tblspace tblspace
in the root dbspace is always 0x1000001. This means that the root space
tblspace tblspace is always contained in the first dbspace and on logical page
1 within the tblspace tblspace. (The bit-map page is page 0.)
tblspace Tblspace Size
The tblspace tblspace pages are allocated as an extent when the dbspace is
initialized.
Usually, the initial size of the tblspace tblspace is 2 percent of the initial
chunk, plus five pages. However, this is not the case if the initial chunk is so
large that the resulting tblspace tblspace would be bigger than a single bit-
map page could manage. In this circumstance, the tblspace tblspace is sized
according to the maximum number of pages that the single bit-map page can
manage.
If a database server process attempts to create a table and the tblspace
tblspace is full, the server process allocates a next extent to the tblspace.
Additional bit-map pages are allocated as needed.
When a table is removed from the dbspace, its corresponding entry in the
tblspace tblspace is deleted. The space in the tblspace is released and can be
used by a new tblspace.
Figure 2-19
The tblspace
number is
composed of the
dbspace number
and a page number
in the tblspace
tblspace.
0
31
23
0 - 23 page number within the tblspace tblspace
24 - 31 dbspace number
Tblspace number