PURPOSE: The RECORD LOCKS option controls whether access requests to a DS are queued or not.
SYNTAX
{ENABLE; DISABLE} RECORD LOCKS [IF; UNLESS clause]
|
ENABLE |
sets up the Simple Queued environment for DS access. When more than one user tries to access a DS, their requests are queued in the order they are received. It allows for multi-user input and single user updating. The queuing is done only on the record level (unlike the Concurrent Queued environment which queues at both the record and table levels). |
|
DISABLE |
returns DS accessing to the default environment. This is the default state. |
|
IF; UNLESS |
specifies a condition for the option to be enabled or disabled. |
Example
*ENABLE RECORD LOCKS...*DISABLE RECORD LOCKSNOTES: Table 14-2 illustrates DS accessing with RECORD LOCKS enabled for all users (assuming no other queued environments are established by any of the users).
|
JOB
|
ACCESS
FOR
|
DATA
SET IS
|
JOB
IS
|
|
1
|
Update
|
open
|
running
|
|
2
|
Input
|
open
|
running
|
|
3
|
Input
|
open
|
running
|
|
4
|
Update
|
open
|
queued
|
|
5
|
Input
|
open
|
queued
|
|
6
|
Supersede
|
busy
|
waiting
|
|
7
|
Input
|
open
|
queued
|
Table 14-2 Simple Queued Environment
All the jobs requested access to the same DS. The request order is reflected by the job numbers. While Job 1 has the DS opened for update, only Jobs 2 and 3 can concurrently access it for input (reading data).
Job 4 has successfully opened the DS and is queued. It will be allowed access when Job 1 releases the DS, since RECORD LOCKS permits only one user to update (write to a record) at a time.
Jobs 5 and 7 could run concurrent with Job 1 but can not "jump" past Job 4. They are queued and will start when Job 4 starts.
Job 6 is attempting to supersede the DS. ACCENT R does not queue this request. (Job 7 appears right behind Job 5 in the queue.) Job 6 must wait and try again periodically until all jobs (including new ones that may come in before the current jobs in the queue finish) release the DS. Once Job 6 has access, no other job can open the DS until the supersede is finished.
SEE ALSO: RELATE Statement