Reclaim Space in Tablespace using Shrink Command




Benefits regarding to Oracle Documentation :

  • Full table scans will take less time (a table scan will always scan up to the HWM even if space is not used)
  • Better index access takes place because of a smaller B-Tree
  • Space is freed up for other database objects
  • Space below the HWM is released and the HWM is moved down

 Thank you
Osama Mustafa


Open_Cursor Parameter , in this article i will discuss what this parameter do  , I used Oracle Documentation to describe this parameter but in simpler way .

In Oracle Documentation

Open_cursor : specifies the maximum number of open cursors (handles to private SQL areas) a session can have at once. You can use this parameter to prevent a session from opening an excessive number of cursors.

to check in database

SQL> show parameter Open_cursor

NAME                                 TYPE        VALUE
———————————— ———– ——————————
open_cursors                         integer     300

As we see in the last Line , “its prevent Session from opening excessive number of cursor”  how is that !!!

Open_cursor located in shared_pool which is part of SGA ( library Cache) , The benefit of this parameter is to prevent Session clogging CPU with requests .

But what i mean when I set this Parameter to integer , let take the above example :

-Parameter is set to 300
-That mean each session can have  300 cursors

If this session fill the 300 What will happened !!!

 “ora-1000 maximum open cursors exceeded”

On Documentation Oracle Recommended to set this Parameter for high value  for Application usage , if the above error raised and you already set to high Value then make sure your developer is closing their cursor and this is common issue.

SQL> Show parameter cursor

NAME                                      TYPE        VALUE
———————————— ———– ——————————
cursor_sharing                             string      EXACT
cursor_space_for_time                boolean     FALSE
open_cursors                               integer     300
session_cached_cursors               integer     20

But what others Parameter mean,  what each parameter mean lets ask this question what if User or session run query include the same cursor , is it take another space in memory !!!

it dose not make sense , so in this case we use SESSION_CACHED_CURSOR.

regarding to oracle documentation

SESSION_CACHED_CURSOR : its Number of session cursors to cache. Repeated parse calls of the same SQL statement cause the session cursor for that statement to be moved into the session cursor cache.  

you have to know some truth about this parameter :
1) its cache only close cursor which mean if you cursor still opened how could it be cached !!!

2) you can set this parameter > OPEN_CURSOR , NOTHING.

3) if you are not setting this parameter ( Value 0 ) then no cursor will be cached for session . But Wait we said oracle used shared pool in cursor Yes , your cursor will be in SHARED_POOL but session have to find this cursor , so if you set to non zero first thing oracle will do is check SHARED_POOL ( Library cache ) and back to you with result .

After discuss point number 3 we see the main advantage for cache cursor which is better performance , enhance query execution time.

But the shared_pool has limited size so i can’t cache all my cursor , now next parameter will avoid this


Boolean value (TURE|FALSE) each one of them mean something

FALSE : Shared SQL areas can be deallocated from the library cache to make room for new SQL statements.

TRUE : Shared SQL areas are kept pinned in the shared pool , if you are using application contain lot of cursor it will be good to set it to enhance execution time ( to do that shared pool must be large enough to hold all open cursors simultaneously) .

 if i have 3 query each one want to use same cursor how oracle handle this , Parameter number 4 will control that.


CURSOR_SHARING determines what kind of SQL statements can share the same cursors.

this parameter take three value ( FORCE | SIMILAR | EXACT ) i will describe each one of them , Oracle Documentation definition :  

-Forces statements that may differ in some literals, but are otherwise identical, to share a cursor, unless the literals affect the meaning of the statement.

-Similar Causes statements that may differ in some literals, but are otherwise identical, to share a cursor, unless the literals affect either the meaning of the statement or the degree to which the plan is optimized.

-Exact Only allows statements with identical text to share the same cursor.

you can’t imagine how many document you will find if you search on google for this parameter , examples , article and tuning for it.

to set this parameter you have to make sure what you need , understand it.the best way to do that with trying to test it.

Thank you
Osama Mustafa

Change Listener Port (Single Instance)

In this Topic i will discuss how to change listener ports , The Database 10gR2 , Operating System RHEL 5.7  this demonstration will work on any Database or platforms , The Simplest way to change listener Ports

Information :
DB Version :
OS : RHEL 5.7
Listener Name : LISTENER
Old Port : 1521
New Port : 1523

Step one :  Check Listener Status .

The Below screen describe The Old Status For Listener Notice the Port is 1521 (Default One)

Step two : Stop Listener  (lsnrctl stop)

Step three : Use netca command  to Change Listener Port Follow the screens

in below screen you can choose the listener port you want to change .

Step Four : After Close netca GUI listener will start automatically

Step Five : Go to $ORACLE_HOME to change tnsnames.ora that used Old Listener port to new port.

Listener.ora will change automatically via netca GUI so no need to update it .

Step Six : Database will not register atomically after doing the above steps , so you have to set LOCAL_LISTENER Parameter Via Sqlplus like the following , i will post lsrnctl status to confirm what i saying, also notice new port that has been changed .

Now , Sqlplus / as sysdba

I Used Scope=memory to test the connection first  , after test the connection successfully you can change scope = spfile.

Step Seven : Test Connection to make sure Every User will Able To connect .

Thank you
Osama Mustafa

What Oracle Version Digit Mean

The first digit is the most general identifier. It represents a major new version of the software that contains significant new functionality.
Database Maintenance Release Number

The second digit represents a maintenance release level. Some new features may also be included.
Application Server Release Number

The third digit reflects the release level of the Oracle Application Server (OracleAS).
Component-Specific Release Number

The fourth digit identifies a release level specific to a component. Different components can have different numbers in this position depending upon, for example, component patch sets or interim releases.
Platform-Specific Release Number

The fifth digit identifies a platform-specific release. Usually this is a patch set. When different platforms require the equivalent patch set, this digit will be the same across the affected platforms.

Thank you
Osama Mustafa

ora-12705 cannot access nls data files or invalid environment specified

This error appear On Sql developer .

ORA-00604: error occurred at recursive SQL level 1
ORA-12705: Cannot access NLS data files or invalid environment specified

Solution :

Try to add following lines to %SQL_DEV_HOME%\sqldeveloper\bin\sqldeveloper.conf
AddVMOption -Duser.language=en

us depend on your language .
en :  England and so on ….

Thank you
Osama Mustafa


i took this procedure from OTN forum  to convert BLOB to CLOB

v_clob CLOB;
v_varchar VARCHAR2(32767);
v_start PLS_INTEGER := 1;
v_buffer PLS_INTEGER := 32767;

FOR i IN 1..CEIL(DBMS_LOB.GETLENGTH(blob_in) / v_buffer)

v_varchar := UTL_RAW.CAST_TO_VARCHAR2(DBMS_LOB.SUBSTR(blob_in, v_buffer, v_start));

DBMS_LOB.WRITEAPPEND(v_clob, LENGTH(v_varchar), v_varchar);
v_start := v_start + v_buffer;
RETURN v_clob;
END blob_to_clob;

 Example :
Select blob_to_clob(blob_column) from table_name;

Check DataGaurd Role Primary/Standby

Which Database is the primary Database , Which One Is the Standby

Simple Query Will Answer this , The Scenario Like the following I have Data Guard I want to check which one Of these database are Primary Or Standby How Can I do that :

SQL > select database_role from v$database;


The above Output Indicate that you are Now On Primary Database, Different Output for Standby

SQL > select database_role from v$database;


There’s More than One Way
SQL> SELECT controlfile_type FROM V$database;

Output On Primary Database :


On Standby :


Thank you
Osama Mustafa

WARNING: Subscription for node down event still pending

Warning Appear like the following : 
[oracle@sun3 ~]$ cat /u01/app/oracle/product/10.2.0/network/log/listener1.log
19-NOV-2012 14:00:19 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=orcl1)(CID=(PROGRAM=sqlplus@sun3)(HOST=sun3)(USER=oracle))) * (ADDRESS=(PROTOCOL=tcp)(HOST= * establish * orcl1 * 12514
TNS-12514: TNS:listener does not currently know of service requested in connect descriptor
19-NOV-2012 14:01:02 * ping * 0
19-NOV-2012 14:08:34 * service_update * orcl1 * 0
19-NOV-2012 14:18:37 * service_update * orcl1 * 0
WARNING: Subscription for node down event still pending
19-NOV-2012 14:23:32 * (CONNECT_DATA=(CID=(PROGRAM=)(HOST=sun3)(USER=oracle))(COMMAND=status)(ARGUMENTS=64)(SERVICE=LISTENER)(VERSION=169869568)) * status * 0
19-NOV-2012 14:23:59 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=orcl1)(CID=(PROGRAM=sqlplus@sun3)(HOST=sun3)(USER=oracle))) * (ADDRESS=(PROTOCOL=tcp)(HOST= * establish * orcl1 * 12514
TNS-12514: TNS:listener does not currently know of service requested in connect descriptor
19-NOV-2012 14:28:40 * service_update * orcl1 * 0
19-NOV-2012 14:30:38 * (CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=orcl1)(CID=(PROGRAM=sqlplus@sun3)(HOST=sun3)(USER=oracle))) * (ADDRESS=(PROTOCOL=tcp)(HOST= * establish * orcl1 * 12514
TNS-12514: TNS:listener does not currently know of service requested in connect descriptor
19-NOV-2012 14:38:43 * service_update * orcl1 * 0
WARNING: Subscription for node down event still pending

In Listener.ora add the following :


Thank you
osama mustafa

Change Listener Default Name

Step One :

ps -ef | grep tns

oracle    4214     1  0 22:51 ?        00:00:00 /u01/app/oracle/product/10.2.0/db_1/bin/tnslsnr LISTENER -inherit

Step two :

lsnrctl stop LISTENER

[oracle@localhost ~]$ lsnrctl stop

LSNRCTL for Linux: Version – Production on 17-NOV-2012 22:55:41

Copyright (c) 1991, 2010, Oracle.  All rights reserved.

The command completed successfully

Step Three :

Go to $ORACLE_HOME/network/admin and modify Listener.ora

[oracle@localhost ~]$ cd /u01/app/oracle/product/10.2.0/db_1/network/admin/

    (SID_DESC =
      (SID_NAME = PLSExtProc)
      (ORACLE_HOME = /u01/app/oracle/product/10.2.0/db_1)
      (PROGRAM = extproc)

      (ADDRESS = (PROTOCOL = TCP)(HOST = localhost.localdomain)(PORT = 1521))

Step Four :

lsnrctl start OSAMA

Step Five :

SQL> show parameter local_listener

SQL> alter system set local_listener='(address=(protocol=tcp)(host=xx.xx.xx.xx)(port=1521))’;
SQL> alter system register;

Thank you
Osama Mustafa

Dealing With Oracle Traces

This article using Oracle Database 11g , I will post for 10g Later .

How Could I change name for Oracle Trace :

alter session set tracefile_identifier = ‘some_id’;

    SQL> alter session set tracefile_identifier = ‘osama’;

    Session altered.

    SQL> oradebug tracefile_name


maximum size of Oracle Trace File

-By Set max_dump_file_size parameter
– alter session set max_dump_file_size = unlimited;

Finding Oracle Trace File for current session :

     SELECT value
    FROM v$diag_info
    WHERE name = ‘Default Trace File’;

Finding Oracle Trace File for Current Database Process

     SELECT pid, program, tracefile
    FROM v$process;

To find all trace files for the current instance:


and you could use ADRCI features.

Thank you
Osama mustafa