Introduction to Stata 8 - (GRIPS

15. Miscellaneous
15.1. Memory considerations [U] 7
In Intercooled Stata a data set can have a maximum of 2,000 variables (Stata/SE: 32,000).
Stata keeps the entire data set in memory, and the number of observations is limited by the
memory allocated. The memory must be allocated before you open (use) a data set.
As described in section 1.2 the initial default memory is defined in the Stata icon. To change
this to 15 MB, right-click the icon, select Properties, and change the path field text to:
c:\stata\wstata.exe /m15.
If the memory allocated is insufficient you get the message:
no room to add more observations
You may increase the current memory to 25 MB by:
clear // You can't change memory size with data in memory
set memory 25m
You can see the amount of used and free memory by:
memory
compress [R] compress
To reduce the physical size of your data set – and the memory requirements – Stata can
determine the fewest bytes needed for each variable (see section 6.2), and you can safely:
compress
and save the data again (save... , replace). This may reduce the memory need by 80%.
Handling huge data sets
If you are regularly handling huge data sets you may consider:
• to use compress to reduce memory requirements
• to increase your computer's RAM (not expensive)
For instance with 512 Mb RAM you could set memory 400m for Stata, and this would fit
very large data sets, e.g. a million observations with 100 variables. Stata/SE can handle up to
32,000 variables, but memory restrictions otherwise don't differ from Intercooled Stata. SAS
or SPSS might be alternatives.
You might not be able to create the entire Stata data set because of its hugeness. Try to read
one part of the data, compress and save, read the next part of the data, compress and save,
etc., and finally combine (append) the partial data sets (see section 10.6):
/ / c:\dokumenter\p1\gen.aa.do
infix id 1 type 2 sold 4-7 using c:\dokumenter\p1\aa.txt in 1/10000
compress
save c:\tmp\aa1.dta
infix id 1 type 2 sold 4-7 using c:\dokumenter\p1\aa.txt in 10001/20000
compress
append using c:\tmp\aa1.dta
save c:\dokumenter\p1\aa.dta
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