Performance related queries

Performance related queries

1. CPU usage of the USER

Displays CPU usage for each User. Useful to understand database load by user.

SELECT ss.username, se.SID, VALUE / 100 cpu_usage_seconds     FROM v$session ss, v$sesstat se, v$statname sn    WHERE     se.STATISTIC# = sn.STATISTIC#          AND NAME LIKE '%CPU used by this session%'          AND se.SID = ss.SID          AND ss.status = 'ACTIVE'          AND ss.username IS NOT NULL ORDER BY VALUE DESC;

2. Long Query progress in database

Show the progress of long running queries.

SELECT a.sid,          a.serial#,          b.username,          opname OPERATION,          target OBJECT,          TRUNC (elapsed_seconds, 5) "ET (s)",          TO_CHAR (start_time, 'HH24:MI:SS') start_time,          ROUND ( (sofar / totalwork) * 100, 2) "COMPLETE (%)"     FROM v$session_longops a, v$session b    WHERE     a.sid = b.sid          AND b.username NOT IN ('SYS', 'SYSTEM')          AND totalwork > 0 ORDER BY elapsed_seconds;

3. Get current session id, process id, client process id?

This is for those who wants to do some voodoo magic using process ids and session ids.

SELECT b.sid,        b.serial#,        a.spid processid,        b.process clientpid   FROM v$process a, v$session b  WHERE a.addr = b.paddr AND b.audsid = USERENV ('sessionid');

• V$SESSION.SID AND V$SESSION.SERIAL# is database process id
• V$PROCESS.SPID is shadow process id on this database server
• V$SESSION.PROCESS is client PROCESS ID, ON windows it IS : separated THE FIRST # IS THE PROCESS ID ON THE client AND 2nd one IS THE THREAD id.
3. Last SQL Fired from particular Schema or Table:

SELECT CREATED, TIMESTAMP, last_ddl_time   FROM all_objects  WHERE     OWNER = 'MYSCHEMA'        AND OBJECT_TYPE = 'TABLE'        AND OBJECT_NAME = 'EMPLOYEE_TABLE';

5. Find Top 10 SQL by reads per execution

SELECT *   FROM (  SELECT ROWNUM,                  SUBSTR (a.sql_text, 1, 200) sql_text,                  TRUNC (                     a.disk_reads / DECODE (a.executions, 0, 1, a.executions))                     reads_per_execution,                  a.buffer_gets,                  a.disk_reads,                  a.executions,                  a.sorts,                  a.address             FROM v$sqlarea a         ORDER BY 3 DESC)  WHERE ROWNUM < 10;

6. Oracle SQL query over the view that shows actual Oracle connections.

SELECT osuser,          username,          machine,          program     FROM v$session ORDER BY osuser;

7. Oracle SQL query that show the opened connections group by the program that opens the connection.

SELECT program application, COUNT (program) Numero_Sesiones     FROM v$session GROUP BY program ORDER BY Numero_Sesiones DESC;

8. Oracle SQL query that shows Oracle users connected and the sessions number for user

SELECT username Usuario_Oracle, COUNT (username) Numero_Sesiones     FROM v$session GROUP BY username ORDER BY Numero_Sesiones DESC;

9. Get number of objects per owner

SELECT owner, COUNT (owner) number_of_objects     FROM dba_objects GROUP BY owner ORDER BY number_of_objects DESC;

Base Tutorial :: basetutorial: Database Administration Queries

Base Tutorial :: basetutorial: Database Administration Queries: Database administration queries Database version information Returns the Oracle database version. SELECT * FROM v$vers...

Database Administration Queries

Database administration queries

1. Database version information

Returns the Oracle database version.

SELECT * FROM v$version;

2. Database default information

Some system default information.

SELECT username,        profile,        default_tablespace,        temporary_tablespace   FROM dba_users;

3. Database Character Set information

Display the character set information of database.

SELECT * FROM nls_database_parameters;

4. Get Oracle version

SELECT VALUE   FROM v$system_parameter  WHERE name = 'compatible';

5. Store data case sensitive but to index it case insensitive

Now this ones tricky. Sometime you might querying database on some value independent of case. In your query you might do UPPER(..) = UPPER(..) on both sides to make it case insensitive. Now in such cases, you might want to make your index case insensitive so that they don’t occupy more space. Feel free to experiment with this one.

CREATE TABLE tab (col1 VARCHAR2 (10)); CREATE INDEX idx1    ON tab (UPPER (col1)); ANALYZE TABLE a COMPUTE STATISTICS;

6. Resizing Tablespace without adding datafile

Yet another DDL query to resize table space.

ALTER DATABASE DATAFILE '/work/oradata/STARTST/STAR02D.dbf' resize 2000M;

7. Checking autoextend on/off for Tablespaces

Query to check if autoextend is on or off for a given tablespace.

SELECT SUBSTR (file_name, 1, 50), AUTOEXTENSIBLE FROM dba_data_files; (OR) SELECT tablespace_name, AUTOEXTENSIBLE FROM dba_data_files;

8. Adding datafile to a tablespace

Query to add datafile in a tablespace.

ALTER TABLESPACE data01 ADD DATAFILE '/work/oradata/STARTST/data01.dbf'     SIZE 1000M AUTOEXTEND OFF;

9. Increasing datafile size

Yet another query to increase the datafile size of a given datafile.

ALTER DATABASE DATAFILE '/u01/app/Test_data_01.dbf' RESIZE 2G;

10. Find the Actual size of a Database

Gives the actual database size in GB.

SELECT SUM (bytes) / 1024 / 1024 / 1024 AS GB FROM dba_data_files;

11. Find the size occupied by Data in a Database or Database usage details

Gives the size occupied by data in this database.

SELECT SUM (bytes) / 1024 / 1024 / 1024 AS GB FROM dba_segments;

12. Find the size of the SCHEMA/USER

Give the size of user in MBs.

SELECT SUM (bytes / 1024 / 1024) "size"   FROM dba_segments  WHERE owner = '&owner';

13. Last SQL fired by the User on Database

This query will display last SQL query fired by each user in this database. Notice how this query display last SQL per each session.

SELECT S.USERNAME || '(' || s.sid || ')-' || s.osuser UNAME,          s.program || '-' || s.terminal || '(' || s.machine || ')' PROG,          s.sid || '/' || s.serial# sid,          s.status "Status",          p.spid,          sql_text sqltext     FROM v$sqltext_with_newlines t, V$SESSION s, v$process p    WHERE     t.address = s.sql_address          AND p.addr = s.paddr(+)          AND t.hash_value = s.sql_hash_value ORDER BY s.sid, t.piece;

Data dictionary queries

Data dictionary queries

1.      Check if a table exists in the current database schema

A simple query that can be used to check if a table exists before you create it. This way you can make your create table script rerunnable. Just replace table_name with actual table you want to check. This query will check if table exists for current user (from where the query is executed).

SELECT table_name   FROM user_tables  WHERE table_name = 'TABLE_NAME';

2.      Check if a column exists in a table

Simple query to check if a particular column exists in table. Useful when you tries to add new column in table using ALTER TABLE statement, you might wanna check if column already exists before adding one.

SELECT column_name AS FOUND   FROM user_tab_cols  WHERE table_name = 'TABLE_NAME' AND column_name = 'COLUMN_NAME';

3.      Showing the table structure

This query gives you the DDL statement for any table. Notice we have pass ‘TABLE’ as first parameter. This query can be generalized to get DDL statement of any database object. For example to get DDL for a view just replace first argument with ‘VIEW’ and second with your view name and so.

SELECT DBMS_METADATA.get_ddl ('TABLE', 'TABLE_NAME', 'USER_NAME') FROM DUAL;

4.      Getting current schema

Yet another query to get current schema name.

SELECT SYS_CONTEXT ('userenv', 'current_schema') FROM DUAL;

5.      Changing current schema

Yet another query to change the current schema. Useful when your script is expected to run under certain user but is actually executed by other user. It is always safe to set the current user to what your script expects.

ALTER SESSION SET CURRENT_SCHEMA = new_schema;