The ENABLE_OPT_TRACE procedure enables full optimizer tracing. After it is enabled, the tracing process will be performed for each plan generation in the current session, including the plan generation process of SQL statements within PL/SQL blocks. A tracing file will be 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 trace only specific SQL statements within PL/SQL functions during the current test, you can set the sql_id parameter. Once sql_id is set, only the specified SQL statements will be traced; otherwise, all SQL statements will be traced. |
| identifier | Specifies the suffix of the trace file, making it easier for users to locate their trace files. |
| level | Specifies the tracing level:
Note: level is a database keyword. In an Oracle-compatible tenant, it must be enclosed in double quotation marks (""). In a MySQL-compatible tenant, it must be enclosed in backticks (`). |
Examples
Enable optimizer tracing for the current session.
/* Connect to the database and enable optimizer tracing for the current session */
obclient> CALL DBMS_XPLAN.ENABLE_OPT_TRACE();
Query OK, 0 rows affected
/* Set the trace log level and file suffix */
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 log 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 optimizer tracing for the current session */
obclient> CALL DBMS_XPLAN.DISABLE_OPT_TRACE();;
Query OK, 0 rows affected