SPSS® 12.0 Command Syntax Reference

CACHE
CACHE.
Although the virtual active file can vastly reduce the amount of temporary disk space
required, the absence of a temporary copy of the "active" file means that the original data
source has to be re-read for each procedure. For data tables read from a database source this
means the SQL query that reads the information from the database must be re-executed for
any command or procedure that needs to read the data. Since virtually all statistical analysis
procedures and charting procedures need to read the data, the SQL query is re-executed for
each procedure you run, which can result in a significant increase in processing time if you
run a large number of procedures.
If you have sufficient disk space on the computer performing the analysis (either your local
computer or a remote server), you can eliminate multiple SQL queries and improve
processing time by creating a data cache of the active file with the CACHE command. The
CACHE command tells SPSS to copy all the data to a temporary disk file the next time the
data are passed to run a procedure. If you want the cache written immediately, use the
EXECUTE command after the CACHE command.
• The only specification is the command name CACHE.
• A cache file will not be written during a procedure which uses temporary variables.
• A cache file will not be written if the data are already in a temporary disk file and that
file has not been modified since it was written.
Example
CACHE.
TEMPORARY.
RECODE alcohol(0 thru .04 = ’sober’) (.04 thru .08 = ’tipsy’)
(else = ’drunk’) into state.
FREQUENCIES var=state.
GRAPH...
No cache file will be written during the FREQUENCIES procedure. It will be written during
the GRAPH procedure.
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