Tuesday, November 24, 2009

Oracle SPFILE and PFILE

Oracle provides two different parameter files, PFILE and SPFILE.

PFILE is a text based file and in order to add/modify any database parameters, need to edit the INIT.ORA file using “vi” in unix or notepad in windows. To apply new or modified database parameters changes, database restart is required.

SPFILE is a binary file and introduced in Oracle 9i. SPFILE simplifies administration, maintaining parameter settings consistent and Server parameter file is a binary file let you make persistent changes to individual parameters. Use the CREATE SPFILE statement to create a Server Parameter file from PFILE with SYSDBA/SYSOPER privilege.

By default PFILE or SPFILE default location is “$ORACLE_HOME/dbs” for UNIX and LINUX, %ORACLE_HOME%\database for Windows. In case of RAC, SPFILE located on the shared storage.

You can change the SPFILE parameters using Enterprise manager or ALTER SYSTEM SET ‘parameter’ statement with SCOPE clause. The SCOPE clause has three values MEMORY, SPFILE and BOTH.

SPFILE: The change is applied in the server parameter file only and is effective at the next startup.
For Ex: - SQL> ALTER SYSTEM SET SGA_MAX_SIZE=1024m SCOPE=spfile;

Memory: The change is applied in memory only and the effect is immediate.
For Ex:- SQL> ALTER SYSTEM SET JOB_QUEUE_PROCESSES=50 SCOPE=MEMORY;

BOTH: The change is applied in both the server parameter file and memory. For dynamic parameters the effect is immediate.
Ex: - SQL> ALTER SYSTEM SET SGA_TARGET=1024m SCOPE=BOTH;

For Static parameters the MEMROY, BOTH specifications are not allowed. Only SPFILE is allowed.

If you do not specify the SCOPE clause then the default is BOTH. For Dynamic parameters you can specify DEFERRED keyword and the specified change is effective only for future sessions.

During Database startup Oracle searches for initialization parameter file under $ORACLE_HOME/dbs in UNIX and $ORACLE_HOME/database on Windows in following order.

spfileSID.ora
spfile.ora
initSID.ora
init.ora

Backup/Restore parameter files(SPFILE and PFILE):
Using Recovery Manager(RMAN), SPFILE can be backed up with database control file by setting
RMAN> CONFIGURE CONTROLFILE AUTOBACKUP ON;
SPFILE can be restored using following RMAN command.
RMAN> RESTORE CONTROLFILE FROM AUTOBACKUP;

PFILE cannot be backed-up using RMAN, backup and restore can be done using O/S copy command.

Common Errors and solutions in modifying SPFILE:
1. SQL>alter system SET LOG_ARCHIVE_DEST='/oradata/TESTDB' scope=both;
alter system SET LOG_ARCHIVE_DEST='/oradata/ TESTDB' scope=both
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-16018: cannot use LOG_ARCHIVE_DEST with LOG_ARCHIVE_DEST_n or
DB_RECOVERY_FILE_DEST

Solution: OCATION keyword is required.
SQL> alter system set log_archive_dest_1='location=/oradata/ TESTDB' scope=both;
System altered.

2. SQL> alter system set log_archive_dest_1='location=/oradta/ TESTDB' scope=both;
alter system set log_archive_dest_1='location=/oradata/ TESTDB' scope=both
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-16032: parameter LOG_ARCHIVE_DEST_1 destination string cannot be translated
ORA-07286: sksagdi: cannot obtain device information.
Linux-x86_64 Error: 2: No such file or directory

Solution: LOG_ARCHIVE_DEST_1 is incorrect or does not exist. Prove correct path.

Regards,
Satishbabu Gunukula
http://www.oracleracexpert.com

Send EMAIL using UTL_MAIL in Oracle 10g

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Thursday, November 12, 2009

How to restore a database to Point in Time using RMAN

You can recover whole database to a specific SCN, time or log sequence number using RMAN, this is called incomplete recovery or point-in-time Recovery (DBPITR).

You must restore all data files from backups create prior to the time to which you want to recovery and you must open database with RESETLOGS option when completes. Please note that RESETLOGS operation creates a new incarnation of the database.

Usually incomplete recovery will be performed under following situations:
1. Corrupt or destroy of some or all online redo logs due to media failure
2. User error causes data loss, for ex accidental drop of a table
3. Archive log missing and you cannot able to perform incomplete recovery
4. Loss of current control file and must use a backup control file to open database.



Follow the steps to recover the database until a specified SCN, time or log sequence

Step 1: Shutdown and startup mount
SQL> SHUTDOWN IMMEDAITE;
SQL> STARTUP MOUNT;

Step 2: Determine the SCN, time or log sequence that you want to recovery the
SCN – you can get the SCN from alert.log file
Sequence – v$log_history

3. Perform the incomplete recovery
If specifying a time, then set NLS_LANG and NLS_DATE_FORMAT environment variables.

RUN
{
SET UNTIL TIME 'Aug 10 2009 11:00:00';
# SET UNTIL SCN 100; # alternatively, specify SCN
# SET UNTIL SEQUENCE 123; # alternatively, specify log seq
RESTORE DATABASE;
RECOVER DATABASE;
}

4. Open database with resetlogs
SQL> ALTER DATABASE OPEN RESETLOGS;

Regards,
Satishbabu Gunukula
http://www.oracleracexpert.com/

Oracle ODBC, OCI, OCCI Drivers, Downloads and Documentation

Oracle ODBC(Open Database Connectivity):
The Oracle ODBC Driver provides access to Oracle databases for applications written using the ODBC interface. With ODBC you can access the Oracle database using .NET, applications from any .NET programming language.

Download Oracle ODBC Driver
http://www.oracle.com/technology/software/tech/windows/odbc/index.html

Oracle ODBC Documentation
http://www.oracle.com/technology/docs/tech/windows/odbc/index.html

Please see the Oracle ODBC Driver discussion forum for any questions/issues.
http://forums.oracle.com/forums/forum.jsp?forum=145

Oracle Call Interface(OCI):
The Oracle Call Interfaces (OCI) is a set of low-level APIs (Application Programming Interface Calls) used to interact with the Oracle Database. It allows one to use operations like logon, execute, parse, fetch, etc.

Download Oracle Call Interface (OCI)
http://www.oracle.com/technology/tech/oci/instantclient/index.html

Please see the below link for OCI documentation
http://download.oracle.com/docs/cd/B19306_01/appdev.102/b14250/toc.htm

Please see the OCI (Oracle Call Interface) Discussion forum for any questions/issues
http://forums.oracle.com/forums/forum.jspa?forumID=67

Oracle C++ Call Interface:
Oracle C++ Call Interface (OCCI) is a high-performance and comprehensive API to access the Oracle database and used for client-server, middle-tier, and complex object modeling applications.

Download OCCI for Linux/Windows
http://www.oracle.com/technology/tech/oci/occi/occidownloads.html

Please see the below link for documentation
http://download.oracle.com/docs/cd/B28359_01/appdev.111/b28390/toc.htm

Please see the C++ Call Interface (OCCI) Discussion forum for any questions/issues.
http://forums.oracle.com/forums/forum.jspa?forumID=168

Regards,
Satishbabu Gunukula
http://www.oracleracexpert.com/