When attempting to update a DBMS table with a MODIFY statement in a DATA Step using the SAS/ACCESS LIBNAME engine, you may receive the following error:

ERROR: File libref.tablename is sequential. This task requires reading observations in a random order, but the engine allows only sequential access.

You must specify the LIBNAME option REREAD_EXPOSURE=YES on the LIBNAME statement. For example:

libname ora oracle user=xx password=yyy path=zzz reread_exposure=yes;