SQL/MX Programming Manual for C and COBOL (G06.24+, H06.03+)

Name Resolution, Similarity Checks, and Automatic
Recompilation
HP NonStop SQL/MX Programming Manual for C and COBOL—523627-004
8-13
Recommended Recompilation Settings for OLTP
Programs
To return recompilation warning messages directly to the program, use a CONTROL
QUERY DEFAULT statement with the RECOMPILATION_WARNINGS option set to
ON:
CONTROL QUERY DEFAULT RECOMPILATION_WARNINGS 'ON';
If the similarity check fails and RECOMPILATION_WARNINGS is ON, the SQL/MX
executor returns warning message 8579 to the program. If a DML statement is
automatically recompiled and RECOMPILATION_WARNINGS is ON, the SQL/MX
executor returns warning message 8576 to the program.
Recommended Recompilation Settings for OLTP Programs
For optimal performance of OLTP programs in a production environment, use these
settings:
A similarity check is faster than automatic recompilation and can reduce the
performance costs of automatic recompilation. Therefore, you should enable similarity
checks for OLTP programs.
Because automatic recompilation incurs a performance cost, it is unsuitable for OLTP
programs and should be disabled. If you allow automatic recompilations but control the
database environment to prevent them from occurring, you should monitor the EMS log
for warning events that indicate that an automatic recompilation has occurred. You can
also turn on the RECOMPILATION_WARNINGS option to report recompilation warning
messages directly to the program when they occur.
For more information, see Similarity Check on page 8-8 and Automatic Recompilation
on page 8-12.
Default Attribute Value
SIMILARITY_CHECK ON
RECOMPILATION_WARNINGS OFF
AUTOMATIC_RECOMPILATION OFF