Information

Title	Why does the _Lock table have records where _Lock-Usr = ?

URL Name	000044741

Article Number	000166343

Environment	Product: Progress Version: 9.x Product: OpenEdge Version: 10.x, 11.1, 11.2, 11.3 OS: All supported platforms

Question/Problem Description

Why does the _Lock table have records where _Lock-Usr = ?
What does it mean if _Lock._Lock-Usr = ?
If the value of _Lock.Lock-Usr is undefined, why it not necessary to process any further records?

Steps to Reproduce

Clarifying Information

Virtual system tables (VSTs), including the _Lock table, are in-memory data structures with the "structure" or representation of a database table. They are not real database tables or temp-tables.

Several Progress articles on the subject of the _Lock table contain sample code that leaves a "FOR EACH _Lock" block when "_Lock._Lock-Usr = ?".

Error Message

Defect Number

Enhancement Number

Cause

Resolution

The _Lock table has a number of "records" equal to -L, whether those locks are used or not. The internal DB structure which represents the _Lock table is allocated all at once, like an array.
_Lock._Lock-Usr = ? means the lock "record" is currently not in use. Several other fields are set to ? as well (e. g. _Lock-Recid).

Unused locks will all always be at the end of the table - there will not be a used "record" after the first one that reports unknowns.

Workaround

Notes

This behavior changed starting with OpenEdge 11.4. In current releases the ordering of the locks is no longer guaranteed.
See article Entries in _Lock no longer appear at top of resultset from OpenEdge 11.4 onward for more details.

References to Other Documentation:

Progress Articles:
How to determine which users are holding record locks on a specific table
How to find who is locking what table(s) using 4GL
How to monitor locks using VST?
Accessing _Lock VST takes a long time
Entries in _Lock no longer appear at top of resultset from OpenEdge 11.4 onward

Keyword Phrase

Last Modified Date	11/20/2020 7:30 AM