Additional Features
Using the IBUFSIZE= System Option
Beginning with SAS 9,
you can use the IBUFSIZE= system option to specify the page size for
an index file. Typically, you do not need to specify an index page
size. However, you might need to use the IBUFSIZE= option if you have
the following:
-
your application is experiencing a lot of I/O in the index file
-
the length of an index value is very large
The main resource that
is saved when reducing levels in the index is I/O. If your application
is experiencing a lot of I/O in the index file, increasing the page
size might help. However, you must re-create the index file after
increasing the page size. The number of pages that are required for
the index varies with the page size, the length of the index value,
and the values themselves.
|
General form, IBUFSIZE=
system option:
IBUFSIZE= MAX | n;
MAX
sets the page size
for an index file to the maximum possible number. For IBUFSIZE=, the
maximum value is 32,767 bytes.
n
specifies the page
size in bytes.
|
CAUTION:
The MIN
setting should be avoided.
When an index is used
to process a request, such as for WHERE processing, SAS searches the
index file in order to rapidly locate the requested record or records.
The page size affects the number of levels in the index. The more
pages there are, the more levels in the index. The more levels, the
longer the index search takes. Increasing the page size allows more
index values to be stored on each page, thus reducing the number of
pages (and the number of levels).
Use IBUFSIZE=0 to reset
the index page size to the default value in your operating environment.
Note: For details about using the
IBUFSIZE= system option, see the SAS documentation.
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