Archive for October, 2018

To Whom I am the master Ali is the the Master

October 15th, 2018, posted in Nusrat Fateh Ali Khan Songs, Sufism
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Man kunto Maula, fa haza Ali un Maula,to whom I am the master, Ali is the the Master,imam ali,hazrat ali,nafak,

Man kunto Maula, fa haza Ali un Maula !!
to whom I am the master. Ali is the the Master. ❤

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Saying of Imam Sajjad About Sujood

October 11th, 2018, posted in Islamic Teachings
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Saying of Imam Sajjad,Imam Sajjad,Islam, islamic teaching,muslims,muslim,Allah,Only Allah

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Oracle Database : How to Shutdown Oracle Database – Shutdown Basics

October 3rd, 2018, posted in Oracle Queries
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Oracle Database and Instance

The Database is a set of physical operating system files. These files actually holds the user data and the metadata (or the data dictionary). Every running Oracle database is associated with (atleast) an Oracle instance. The Instance refers to the set of Oracle background processes or threads and a shared memory area (SGA). An instance can mount and open at most one database in its life. A database may be mounted and opened by one or more instances (using RAC) and the number of instances mounting a single database can fluctuate over time.Problem sys@standby> startup mount; ORACLE instance started. Total System Global Area 835104768 bytes Fixed Size 2217952 bytes Variable Size 490735648 bytes Database Buffers 335544320 bytes Redo Buffers 6606848 bytes Database mounted. sys@standby> alter database recover managed standby database using current logfile disconnect; alter database recover managed standby database using current logfile disconnect * ERROR at line 1: ORA-01153: an incompatible media recovery is active Cause This indicates a currently running media recovery process. Action sys@standby> alter database recover managed standby database cancel; sys@standby> alter database recover managed standby database using current logfile disconnect; Note When shutting down physical standby database, firstly turn off media recovery process. Otherwise the next time when starting up redo apply again, you will encounter error ORA-01153.

Database Shutdown

During a database shutdown we close the database and terminates the instance.

Different Modes in Database Shutdown
There are different modes to bring down the database:
1. Shutdown immediate
2. Shutdown transactional
3. Shutdown normal
4. Shutdown abort
No user session will be permitted once you issue any of these Shutdown commands.


Shutdown Immediate

– Oracle Database terminates any executing SQL statements and disconnects users.
– Active transactions are terminated and uncommitted changes are rolled back.
– Oracle then performs a checkpoint and then close the online datafiles.

$ sqlplus / as sysdba
SQL> shutdown immediate


Shutdown Transactional

– This mode prevents users from starting new transactions, but waits for all current transactions to complete before shutting down.
– Oracle then performs a checkpoint and then close the online datafiles.

$ sqlplus / as sysdba
SQL> shutdown transactional


Shutdown Normal

– The database waits for all connected users to disconnect before shutting down.
– It waits till all the current transactions end.
– Oracle then performs a checkpoint and then close the online datafiles.

$ sqlplus / as sysdba
SQL> shutdown normal


Shutdown Abort

– Oracle Closes the datafiles without any checkpoint.
– This is the fastest shutdown mode.
– Instance recovery is required in the next startup and hence it will take time.

$ sqlplus / as sysdba
SQL> shutdown abort



Different Phases in Database Shutdown


Close the Database

– Oracle writes the data in the SGA to the disk, updates the file headers and closes the online datafiles and the redo log files.
– But the database will still be mounted.

Dismount the Database

– After the database is closed, Oracle Database unmounts the database to disassociate it from the instance.
– After a database is unmounted, Oracle Database closes the control files of the database.
– At this point, the instance remains in memory.

Shutdown the Instance

– The last step is to remove the shared memory (SGA) and terminate the background processes.
Sometimes shutdown does not cleanup the SGA or background process completely. This can cause error during the next startup. In such situation we can force a instance startup

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Oracle Database : How to Startup Oracle Database – Startup Basics

October 1st, 2018, posted in Oracle Queries
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Oracle Database and Instance

The Database is a set of physical operating system files. These files actually holds the user data and the metadata (or the data dictionary). Every running Oracle database is associated with (atleast) an Oracle instance. The Instance refers to the set of Oracle background processes or threads and a shared memory area (SGA). An instance can mount and open at most one database in its life. A database may be mounted and opened by one or more instances (using RAC) and the number of instances mounting a single database can fluctuate over time.

Database statup

For any normal user to access the database, the instance has to be started up and it should mount and open the corresponding database. We term the entire steps as database startup. In short, database startup includes the following steps:

1. Start an instance.
2. Mount the database.
3. Open the database.

Database startup requires SYSDBA privilege. To start a database :

$ export ORACLE_SID=[SID of the instance]
$ export ORACLE_HOME= [location of ORACLE_HOME]
$ sqlplus / as sysdba
SQL> startup

The above syntax assumes you have a pfile or spfile in the default location ($ORACLE_HOME/dbs). If you are using a non default parameter file, the startup command is:

$ sqlplus / as sysdba
SQL> startup pfile=[file name and location]



Nomount stage

When you issue a ‘Startup’ command, this is the first stage. ie, starting up the instance. Here,
– Oracle will read the parameter file (spfile or pfile) in the default location or in the location specified in the startup command.
– It will then allocate the memory area (SGA) and starts the background processes. Together we call it as the instance.
– Please note that no database is associated with the instance at this point. We can start the instance alone using the command:

$ sqlplus / as sysdba
SQL> startup nomount
ORACLE instance started.

Total System Global Area 304807936 bytes
Fixed Size 2221000 bytes
Variable Size 113249336 bytes
Database Buffers 184549376 bytes
Redo Buffers 4788224 bytes

The instance is now started and the database is in nomount stage. Starting the instance in nomount stage is usually required for database creation or for creating or recovering the controlfiles.


Mount stage

– In this phase the instance will mount the database.
– Mounting the instance means associating the started instance with a specified database.
– For this, the instance checks the controlfiles specified under CONTROL_FILES parameter and opens it.
– It then reads the control files to find the names of the data files and the online redo log files that it will attempt to access when opening the database.
– The database is still closed and only the DBA can access it.
– This stage is normally used for maintenance operations like renaming datafiles, enabling and disabling archiving options.
– Adding, dropping, or renaming redo log files is also done in mount stage.
– For performing full database recovery database is opened in mount stage.

To mount a database:

$ sqlplus / as sysdba
SQL> startup mount

To mount a database from nomount stage:

$ sqlplus / as sysdba
SQL> alter database mount



Open stage

– This is the final stage and here Oracle opens the online datafiles and redolog files.
– If any of the required files are not present, media recovery is required .
– It also ensures the datafiles are consistent. Incase of a normal shutdown, the in-memory changes will be written to disk as part of the shutdown checkpoint.
– But if the instance crashed (or shutdown abort), then Oracle Database performs the instance recovery in the next startup.Oracle : Size Of Database,Oracle,Size Of Database,Database,data files, redo log files, control files, temporary files,Oracle data files,Oracle redo log files,Oracle control files,Oracle temporary files,Enabling And Checking the Status of Flashback On Database,Oracle Database,Oracle DBA,Enabling Flashback On Database,Checking the Status of Flashback On Database, Status of Flashback On Database, Enable Flashback On Database, Enabling Flashback On Database,Enable Flashback On Oracle Database, Enabling Flashback On Oracle Database,

To open a database :

$ sqlplus / as sysdba
SQL> startup

To open a database from mount stage:

$ sqlplus / as sysdba
SQL> alter database open

To verify :

SQL> select open_mode from v$database;

OPEN_MODE
--------------------
READ WRITE
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