SAS software supports several levels
of data locking, which is a means of holding information constant
so that it does not change unexpectedly. The control level is the
degree to which a SAS procedure can restrict access to data. SAS
procedures can request locks on individual records, on library members,
and so on. Locking is also controlled by the SAS software CNTLLEV
data set option, which can request record-level locking and member-level
locking. Some SAS procedures set CNTLLEV equal to MEM internally
for their own processing reasons. Many statistical procedures must
make multiple passes of the data. For example, finding the median
requires more than one pass.
The
ADABAS interface view engine honors all locking
requests in a multi-user environment. (Locks are not required in
a single-user environment.) The following conditions apply:
-
If there are no locking requests,
you cannot update
ADABAS
data.
-
For record-level locking,
ADABAS locks one
ADABAS logical record at a time. If the record
contains a periodic group, the lock includes one or more SAS observations.
-
For member-level locking,
ADABAS puts a hold on the entire
ADABAS file.