Information for the Database Administrator

Controlling Data Locks with ADABAS

SAS software supports several levels of data locking, which is a means of holding information constant so that it doesn't 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 will include one or more SAS observations.
For member-level locking, ADABAS puts a hold on the entire ADABAS file.

For more information about how the interface view engine handles locking, see Competitive Updating and Logical Transaction Recovery.

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