The LOCK statement enables you to acquire and release an exclusive lock on an existing SAS^® file. To determine whether a lock can be obtained, execute the MODIFY statement within a DATA step, because it requires a lock on the data set in Update mode.

/* Set macro variable LOCKED to a value of 'yes' */

%let locked=yes;

/* Use a MODIFY statement to determine if the data set is locked   */
/* since it requires locking the data set in update mode at the    */
/* observation level.  In order to lock the data set at the member */
/* level, use the CNTLLEV= option.                                 */ 

data library.data_set_name;
   modify lib.a(cntllev=mem);
/* If the data set is not locked, the following CALL SYMPUTX       */
/* will run and set &LOCKED to 'no'.                               */
   call symputx('locked','no');
   stop;
run;

If you were unable to obtain a lock but want to continue trying to obtain that lock for a period of time, use the code below. The code uses the SLEEP function to attempt a lock periodically.

/* The SLEEP function is used to wait for a lock to be obtained.    */
/* You set the number of seconds that the lock should continue to   */
/* be attempted with the TIMEOUT= parameter.                        */

libname test 'path_to_SAS_data_library';

/* Create a test data set */
data test.f1;
   infile datalines;
   input a b;
   datalines;
1 2
3 4
5 6
7 8
;
run;

/* Options to help debug the macro */
options mprint mlogic symbolgen;

%macro trylock(member=, timeout=);
   %local starttime;
   %let starttime = %sysfunc(datetime());
   %do %until (&syslckrc = 0
       or %sysevalf(%sysfunc(datetime()) > (&starttime + &timeout)));
      %put trying to open ...;
      %put trying lock ...;
      lock &member;
      %if &syslckrc ne 0 %then %let rc=%sysfunc(sleep(15));
      %put syslckrc=&syslckrc;
   %end;
%mend trylock;

%trylock(member=test.f1, timeout=600);

proc print data=test.f1;
run;

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These sample files and code examples are provided by SAS Institute Inc. "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. Recipients acknowledge and agree that SAS Institute shall not be liable for any damages whatsoever arising out of their use of this material. In addition, SAS Institute will provide no support for the materials contained herein.

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These sample files and code examples are provided by SAS Institute Inc. "as is" without warranty of any kind, either express or implied, including but not limited to the implied warranties of merchantability and fitness for a particular purpose. Recipients acknowledge and agree that SAS Institute shall not be liable for any damages whatsoever arising out of their use of this material. In addition, SAS Institute will provide no support for the materials contained herein.

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