SQL/MX 3.x Installation and Management Guide (H06.22+, J06.11+)

HP NonStop SQL/MX Installation and Management Guide—640325-001
6-1
6
Reviewing and Setting System
Defaults
NonStop SQL/MX uses system-defined default settings for attributes associated with
compiling and executing queries. The system-defined default settings, which are
hard-coded settings, are optimal in most cases. Under some circumstances, however,
you might want to override a specific system-defined default setting. System-defined
default settings can be overridden on a system level (affecting all applications) by
inserting a row into the SYSTEM_DEFAULTS table, or in a specific, limited context by
executing any of these statements:
•
CONTROL QUERY DEFAULT
•
CONTROL TABLE
•
SET TABLE
This section identifies the system defaults that are new for SQL/MX Release3.0. It also
identifies those defaults that you should consider changing after you install SQL/MX
Release 3.0 and before you run your applications. Sometimes a setting other than the
default is recommended, but the default itself is not changed to ensure
backward-compatibility with existing applications.
This section addresses these topics:
•
Setting and Updating System Defaults on page 6-1
•
Consequences of Inserting Rows Into the SYSTEM_DEFAULTS Table on page 6-2
For comprehensive information about system defaults and the SYSTEM_DEFAULTS
metadata table, see the SQL/MX Reference Manual.
Setting and Updating System Defaults
The SYSTEM_DEFAULTS table is defined in schema SYSTEM_DEFAULTS_SCHEMA
of catalog NONSTOP_SQLMX_nodename. The SYSTEM_DEFAULTS table contains
only one row, inserted by the InstallSqlmx script for the NATIONAL_CHARSET
default, until you insert additional rows that contain default settings. To update the
SYSTEM_DEFAULTS table, you must be the super ID or a user to whom the super ID
has granted UPDATE privileges. All other users have SELECT privileges on this table.
The statements in this example insert a default into the SYSTEM_DEFAULTS table on
\MYSYS to set the default setting for the transaction isolation level:
SET SCHEMA nonstop_sqlmx_mysys.system_defaults_schema;
INSERT INTO SYSTEM_DEFAULTS
(ATTRIBUTE, ATTR_VALUE)
VALUES ('ISOLATION_LEVEL', 'SERIALIZABLE');