topic Re: Memory usage in SAS in SAS Programming

Memory usage in SAS

SuryaKiran — Thu, 03 Jan 2019 17:20:27 GMT

Hello,

I was trying to understand how memory utilization is done in SAS. SASHELP.CLASS dataset has fize size of 128KB and when trying to print this dataset (PROC PRINT) it is utilizing ~843KB, almost 6 time the its file size. Where as proc sql select utilizing ~3248KB.

1) Why 6 times more?

2) Can we reduce memory usage?

options fullstimer;

proc sql;
create table test as 
select Libname,memname,filesize format=sizekmg.
from dictionary.tables 
where libname='SASHELP' and memname='CLASS';
quit;

proc print data=sashelp.class noobs;
run;

proc sql;
select * from sashelp.class;
quit;

23         options fullstimer;
24         
25         proc print data=sashelp.class noobs;
26         run;

NOTE: There were 19 observations read from the data set SASHELP.CLASS.
NOTE: PROCEDURE PRINT used (Total process time):
      real time           0.02 seconds
      user cpu time       0.01 seconds
      system cpu time     0.00 seconds
      memory              845.78k
      OS Memory           15956.00k
      Timestamp           01/03/2019 12:11:05 PM
      Step Count                        12  Switch Count  24
      

27         
28         proc sql;
29         select * from sashelp.class;
30         quit;
NOTE: PROCEDURE SQL used (Total process time):
      real time           0.02 seconds
      user cpu time       0.01 seconds
      system cpu time     0.00 seconds
      memory              3249.12k
      OS Memory           19032.00k
      Timestamp           01/03/2019 12:11:05 PM
      Step Count                        13  Switch Count  24

Re: Memory usage in SAS

r_behata — Thu, 03 Jan 2019 17:55:16 GMT

Hello @SuryaKiran

Bench marking performance on small data sets can be tricky. Look at the results I have got. Each Re-run gave me a different result.

24         options fullstimer;
25         
26         
27         proc print data=sashelp.class noobs;
28         run;

NOTE: There were 19 observations read from the data set SASHELP.CLASS.
NOTE: PROCEDURE PRINT used (Total process time):
      real time           0.01 seconds
      user cpu time       0.00 seconds
      system cpu time     0.00 seconds
      memory              602.37k
      OS Memory           16424.00k
      Timestamp           01/03/2019 11:47:33 AM
      Page Faults                       0
      Page Reclaims                     8
      Page Swaps                        0
      Voluntary Context Switches        4
      Involuntary Context Switches      4
      Block Input Operations            0
      Block Output Operations           0
      

29         
30         proc sql;
31         select * from sashelp.class;
32         quit;
NOTE: PROCEDURE SQL used (Total process time):
      real time           0.12 seconds
      user cpu time       0.01 seconds
      system cpu time     0.00 seconds
      memory              303.31k
      OS Memory           16424.00k
      Timestamp           01/03/2019 11:47:33 AM
2                                                          The SAS System                            09:57 Thursday, January 3, 2019

      Page Faults                       0
      Page Reclaims                     2
      Page Swaps                        0
      Voluntary Context Switches        25
      Involuntary Context Switches      7
      Block Input Operations            0
      Block Output Operations           0

Re: Memory usage in SAS

SuryaKiran — Thu, 03 Jan 2019 18:51:06 GMT

@r_behata I'm aware that it varies, but my question is why the memory size is very high than its file size?

Re: Memory usage in SAS

ballardw — Thu, 03 Jan 2019 22:00:58 GMT

Part of that is the memory requirements for holding tables in memory while building them for display in HTML/RTF/PDF other destination.

HTML default destination for results open
184  proc print data=sashelp.class;
NOTE: Writing HTML Body file: sashtml3.htm
185  run;

NOTE: There were 19 observations read from the data set SASHELP.CLASS.
NOTE: PROCEDURE PRINT used (Total process time):
      real time           0.64 seconds
      user cpu time       0.21 seconds
      system cpu time     0.26 seconds
      memory              6588.76k
      OS Memory           22772.00k
      Timestamp           01/03/2019 02:57:54 PM
      Step Count                        25  Switch Count  0


186  ods html close;
187  ods listing;
188  %put HTML Closed and List output used.;
HTML Closed and List output used.
189  proc print data=sashelp.class;
190  run;

NOTE: There were 19 observations read from the data set SASHELP.CLASS.
NOTE: PROCEDURE PRINT used (Total process time):
      real time           0.00 seconds
      user cpu time       0.00 seconds
      system cpu time     0.00 seconds
      memory              360.37k
      OS Memory           21492.00k
      Timestamp           01/03/2019 02:57:54 PM
      Step Count                        26  Switch Count  0


191  ods listing close;

Different destinations and style options actually used will affect the numbers.

Re: Memory usage in SAS

SASKiwi — Thu, 03 Jan 2019 22:56:24 GMT

Don't forget the SAS procedure you are using takes up memory too. PROC PRINT is a relatively simple procedure so takes up less memory than PROC SQL which is much more complex with a lot more functionality.