The Geek Diary

Beginners Guide to Monitoring SQL Statements with Real-Time SQL Monitoring in Oracle Database

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The post explains how to use Real-Time SQL Monitoring to monitor queries. The Oracle 11g Database or later versions have a new interface to monitor long-running SQL commands. The feature is called Real-Time SQL Monitoring. By default, SQL monitoring is automatically started when a SQL command runs parallel, or when it has consumed at least five seconds of the CPU or I/O time in a single execution. The MONITOR hint can also be used to turn on SQL Monitoring for a SQL statement.
SQL Monitoring requires:

  • A Diagnostics and Tuning Pack License
  • STATISTICS_LEVEL parameter to be set to ‘TYPICAL’ or ‘ALL’
  • CONTROL_MANAGEMENT_PACK_ACCESS parameter set to ‘DIAGNOSTIC+TUNING’.

The Real-Time SQL Monitoring feature is licensed with Diagnostics and Tuning Pack. After monitoring is initiated, entries are added to the dynamic performance V$SQL_MONITOR and V$SQL_PLAN_MONITOR views. This entry tracks key performance metrics collected for the execution, including the elapsed time, CPU time, number of reads and writes, I/O wait time and various other wait times. These statistics are refreshed in near real-time as the command executes, generally once every second.

After the execution ends, monitoring information is not deleted immediately but is kept in the V$SQL_MONITOR/V$SQL_PLAN_MONITOR view for at least one minute. The entry is eventually deleted so its space can be reclaimed as new commands are monitored.
You can find more details in the attached white paper.

DBMS_SQLTUNE.REPORT_SQL_MONITOR

The REPORT_SQL_MONITOR function is used to return a SQL monitoring report for a specific SQL statement. The SQL statement can be identified using a variety of parameters. The function accepts some optional parameters, the most common ones are:

  • SQL_ID – The SQL_ID of the query of interest. When NULL (the default) the last monitored statement is targeted.
  • REPORT_LEVEL – The amount of information displayed in the report. The basic allowed values are ‘NONE’, ‘BASIC’, ‘TYPICAL’ or ‘ALL’. The default is ‘TYPICAL’ which is sufficent in most cases.
  • TYPE – The format used to display the report (‘TEXT’, ‘HTML’, ‘XML’ or ‘ACTIVE’). The ‘ACTIVE’ parameter is new in Oracle 11g Release 2 and displays the output using HTML and Flash. An Internet connection is needed to use the ‘ACTIVE’ parameter.
  • SESSION_ID – Targets a subset of queries based on the specified SID. Use SYS_CONTEXT(‘USERENV’,’SID’) for the current session. The default is NULL.

Following is an example using REPORT_SQL_MONITOR:

SET LONG 1000000
SET LONGCHUNKSIZE 1000000
SET LINESIZE 1000
SET PAGESIZE 0
SET TRIM ON
SET TRIMSPOOL ON
SET ECHO OFF
SET FEEDBACK OFF

SELECT DBMS_SQLTUNE.report_sql_monitor(sql_id => '', type => 'TEXT')
AS report FROM dual;

To get an overview what SQL commands are in V$SQL_MONITOR you can use:

SET LINESIZE 300
COLUMN sql_text FORMAT A100
SELECT sql_id, status, sql_text FROM v$sql_monitor;

or you can use the function REPORT_SQL_MONITOR_LIST. For the above example this shows that there is a statement with the SQLID 0tqfh0cggfg0v. We can get now a report with the following command:

SET LONG 1000000 
SET FEEDBACK OFF
spool monitor_sql.html 
SELECT DBMS_SQLTUNE.report_sql_monitor(sql_id =>'0tqfh0cggfg0v',type=> 'HTML')
AS report FROM dual;
spool off

The options are TEXT, HTML or ACTIVE. The active option is the best choice for parallel queries. The output looks like this :

HTML:

TEXT:

Real-Time SQL Monitoring

REPORT_SQL_MONITOR_LIST

The REPORT_SQL_MONITOR_LIST function was added in Oracle 11g Release 2 to generate a summary of all SQL stored in V$SQL_MONITOR.

SET LONG 1000000
SET LONGCHUNKSIZE 1000000
SET LINESIZE 1000
SET PAGESIZE 0
SET TRIM ON
SET TRIMSPOOL ON
SET ECHO OFF
SET FEEDBACK OFF

SELECT DBMS_SQLTUNE.report_sql_monitor_list(type =>'TEXT',report_level => 'ALL') AS report FROM dual;

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