请问各位前辈，我现在有一个排序的问题，不知应如何解决?我在进行排序时，无法排序，并出现错误讯息，请问这是代表什么意思，我该如何解决并顺利完成排序呢?

data book5;
set book4;
run;
proc
sort
data=book5;

by date ;
run;

223
proc sort data=book5;
224
by date time;
225
run;

ERROR: Utility file write failed.
Probable disk full condition.
NOTE: The SAS System stopped processing this step because of errors.
NOTE: There were 670977 observations read from the data set WORK.BOOK5.
WARNING: The data set WORK.BOOK5 may be incomplete.
When this step was stopped there were 0 observations and 45 variables.
WARNING: Data set WORK.BOOK5 was not replaced because this step was stopped.
NOTE: PROCEDURE SORT used (Total process time):

real time
7.67 seconds

cpu time
1.45 seconds


226
227
proc sort data=book5;
228
by date ;
229
run;

ERROR: Utility file write failed.
Probable disk full condition.
NOTE: The SAS System stopped processing this step because of errors.
NOTE: There were 684545 observations read from the data set WORK.BOOK5.
WARNING: The data set WORK.BOOK5 may be incomplete.
When this step was stopped there were 0 observations and 45 variables.
WARNING: Data set WORK.BOOK5 was not replaced because this step was stopped.
NOTE: PROCEDURE SORT used (Total process time):

real time
3.82 seconds

cpu time
0.84 seconds