Micro Focus Visual COBOL 2.3 for Visual Studio 2015 > General Reference > COBOL Language Reference > Part 2. Program Definition > Procedure Division > File I/O Concepts > Sharing Files on Multi-user Systems > Default Record Locking

Default Record Locking

Tables 2, 3 and 4 show the default type of locking which is used when files are opened in a particular open mode. The default locking can be modified if the AUTOLOCK Compiler directive was specified at the time the compilation group was submitted to your COBOL system. The tables also indicate whether the default type of locking can be overridden for individual files. This is done by inserting a suitable clause in the SELECT clause for the file. (See the topic The File Control Entry.)

X/Open restricts those X/Open conforming source programs that use locking to either single record locks with automatic locking, or multiple record locks with manual locking.

Table 1. Default Locking For Record Sequential Files
OPEN Mode	No Directive	AUTOLOCK Compiler Directive	Override in SELECT Statement
INPUT	No lock	No lock	Yes, but only to Exclusive
I-O	Exclusive	Lock on single record	Yes
OUTPUT	Exclusive	Exclusive	No
EXTEND	Exclusive	No lock	Yes, the file can be made shareable but no records are locked

Table 2. Default Locking For Line Sequential Files
OPEN Mode	No Directive	AUTOLOCK Compiler Directive	Override in SELECT Statement
INPUT	No lock	No lock	No
I-O	Exclusive	No lock	No
OUTPUT	Exclusive	Exclusive	No
EXTEND	Exclusive	No lock	No

Table 3. Default Locking For Relative And Indexed Files
OPEN Mode	No Directive	AUTOLOCK Compiler Directive	Override in SELECT Statement
INPUT	No lock	No lock	Yes, but only to Exclusive
I-O	Exclusive	Automatic lock on single record	Yes
OUTPUT	Exclusive	Exclusive	No
EXTEND	Exclusive	Exclusive	No

Note:

A file opened for OUTPUT causes the file to become exclusive, regardless of the specified lock mode.
You can select the type of locking for individual files by accepting the default locking (see Tables 1, 2 and 3) or by including a LOCK MODE clause in the file control entry (see the section The File Control Entry).