User Guide

59
Data Files
You can change the file permissions back to read/write by selecting Mark File Read
Write
from the File menu.
Virtual Active File
The virtual active file enables you to work with large data files without requiring
equally large (or larger) amounts of temporary disk space. For most analysis and
charting p
rocedures, the original data source is reread each time you run a different
procedure. Procedures that modify the data require a certain amount of temporary
disk space to keep track of the changes, and some actions always require enough disk
space for a
t least one entire copy of the data file.
Figure 3-24
Temporary disk space re qui rements
COMPUTE v6 = …
RECODE v4…
Action GET FILE = 'v1-5.sav'. REGRESSION… or
FREQUENCIES… /SAVE ZPRED.
v1 v2 v3 v4 v5 v1 v2 v3 v4 v5 v6 zpre v1 v2 v3 v4 v5 v6 zpre
11 12 13 14 15 11 12 13 14 15 16 1 11 12 13 14 15 16 1
Virtual 21 22 23 24 25 21 22 23 24 25 26 2 21 22 23 24 25 26 2
Active 31 32 33 34 35 31 32 33 34 35 36 3 31 32 33 34 35 36 3
File 41 42 43 44 45 41 42 43 44 45 46 4 41 42 43 44 45 46 4
51 52 53 54 55 51 52 53 54 55 56 5 51 52 53 54 55 56 5
61 62 63 64 65 61 62 63 64 65 66 6 61 62 63 64 65 66 6
Data v4 v6 zpre v1 v2 v3 v4 v5 v6 zpre
Stored 1416 1 111213141516 1
in 2426 2 212223242526 2
Temporary 3436 3 313233343536 3
Disk 4446 4 414243444546 4
Space 5456 5 515253545556 5
6466 6 616263646566 6
CACHE
SORT CASES BY…
None
Actions that don’t require any temporary disk space include:
 Reading SPSS data files
 Merging two or more SPSS data files
 Reading database tables with the Database Wizard
 Merging an SPSS data file with a database table
 Running procedures that read data (for example, Frequencies, Crosstabs, Explore)