16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
49 lines
1.2 KiB
Plaintext
49 lines
1.2 KiB
Plaintext
== Why is this an issue?
|
|
|
|
Explicitly defining a cursor as read-only can improve performance by avoiding table locking. This allows other SQL requests to execute in parallel. Therefore when a cursor will only be used to read data, without modifying anything, the ``++FOR READ ONLY++`` clause or its synonyn, ``++FOR FETCH ONLY++``, should be used.
|
|
|
|
|
|
Conversely when a cursor will modify data, that too should be specified using the ``++FOR UPDATE++`` clause.
|
|
|
|
|
|
In short, it's better to always explicitly define the purpose of the cursor with help of the ``++FOR READ ONLY++``, ``++FOR FETCH ONLY++`` or ``++FOR UPDATE++`` clauses.
|
|
|
|
|
|
=== Noncompliant code example
|
|
|
|
[source,cobol]
|
|
----
|
|
EXEC SQL DECLARE CMAJ_0A CURSOR
|
|
FOR SELECT C_BQ
|
|
FROM S1ORDCOU
|
|
WHERE C_BQ = :TORD-C-BQ
|
|
END-EXEC
|
|
----
|
|
|
|
|
|
=== Compliant solution
|
|
|
|
[source,cobol]
|
|
----
|
|
EXEC SQL DECLARE CMAJ_0A CURSOR
|
|
FOR SELECT C_BQ
|
|
FROM S1ORDCOU
|
|
WHERE C_BQ = :TORD-C-BQ
|
|
FOR READ ONLY
|
|
END-EXEC
|
|
----
|
|
|
|
|
|
ifdef::env-github,rspecator-view[]
|
|
|
|
'''
|
|
== Implementation Specification
|
|
(visible only on this page)
|
|
|
|
=== Message
|
|
|
|
Explicitly specify whether the "XXXX" cursor is read-only or not.
|
|
|
|
|
|
endif::env-github,rspecator-view[]
|