The ENABLE_OPT_TRACE procedure enables full-trace of the optimizer. After it is enabled, the plan generation process of each statement in the current session is traced, including the plan generation process of SQL statements in PL/SQL programs, and a trace file is generated in the execution node log directory of the SQL statement.
Syntax
DEFAULT_INENTIFIER constant VARCHAR2(20) := '';
DEFAULT_LEVEL constant INT := 1;
DBMS_XPLAN.ENABLE_OPT_TRACE(
sql_id IN VARCHAR2 DEFAULT '',
identifier IN VARCHAR2 DEFAULT DEFAULT_INENTIFIER,
level IN INT DEFAULT DEFAULT_LEVEL
);
Parameters
| Parameter | Description |
|---|---|
| sql_id | Specifies the SQL statement to be traced. For example, if you want to run a PL/SQL program and trace only specific SQL statements within the PL/SQL functions, you can set the sql_id parameter. Once sql_id is set, only the specified SQL statements are traced; otherwise, all SQL statements are traced. |
| identifier | Specifies the suffix of the trace file, making it easier for users to locate their trace files. |
| level | Specifies the trace level:
Note: level is a database keyword. In Oracle tenants, it must be enclosed in double quotation marks (" "), and in MySQL tenants, it must be enclosed in backticks (` ). |
Examples
Enable the optimizer trace for the current session.
/* Connect to the database and enable the optimizer trace for the current session */
obclient> CALL DBMS_XPLAN.ENABLE_OPT_TRACE();
Query OK, 0 rows affected
/* Set the trace level and the suffix of the trace file */
obclient> CALL DBMS_XPLAN.SET_OPT_TRACE_PARAMETER(identifier=>'trace_test', `level`=>3);
Query OK, 0 rows affected
/* Execute a query */
obclient> SELECT * FROM t1;
Empty set
/* View the trace file with the suffix "trace_test" in the log directory of the OBServer node */
vi /data/1/observer/log/optimizer_trace_BkkGn1_trace_test.trac
/* Disable the optimizer trace for the current session */
obclient> CALL DBMS_XPLAN.DISABLE_OPT_TRACE();;
Query OK, 0 rows affected