What is Oracle Database Architecture ?
It is a combination of Instance and Database.
What is Instance ?
It is a combination of Memory Structure of SGA and Background processes.
SGA ( Shared Global Area) :
* it is a memory area which can be shared by all the users of database.
* SGA has been build with fllowing components.
1. Shared Pool
This has been divided into subcomponents
i. Library Cache
ii. Data Dictionary Cache
i. Libray Cache:
it contains sharable parsed SQL and PL/SQL Statements.
ii. Data Dictionary Cache:
it contains Dictionary Information and a copy of Base tables,the data will be stored in the form of Rows,it is also called Row Cache.
2. DataBase Buffer Cache:
It Stores a copy of user Data or server process stores data before giving to the user.
LRU LIST :
The Data will be stored in the form of Blocks.
WRITE LIST :
The Modified Blocks become Dirty will be ready to move in data files.
3. Log Buffer Cache:
It Stores Redo Entries,Every single Automatic change happen in database it is called redo entry.
4. Large Pool:
it stores rman backup backup information
5. Java Pool:
it is used for executeing or parsing the java programs.
6. Stream Pool:
it is a Memory Area which will be used when oracle streams is implemented.
PGA ( Private Global Area ):
it is a Memory Area when a user statements will be executed and also sorting the statement will be performed in PGA.
parameter of PGA : PGA_AGGREGATE_TARGET
User Process ?
it is a process which will be created on the client side when ever application is started.
Server Process ?
it is the process reside on server side which will do the work on the half of user process.
What are Oracle Background Processes ?
1. SMON
2. PMON
3. DBWR
4. LGWR
5. CKPT
6. ARCHn
7. MMON
8. MMAN
9. CTWR ........etc
1. SMON :
* SMON will do instance recovery.it will be done in three steps,
a. Write the committed transactions to datafiles
b. Open the DataBase for User Access.
c. Rollback the uncommitted transtractions
* SMON Collase the free space in table space.
* SMON will release the temporary segment onces the transactions is completed.
* SMON will have 16 slave processes.
2. PMON :
* PMON will authenticate the user by using Dictionary Information.
* PMON will register the listener with the instance.
* PMON will release locks and resources when the session is abnormally terminated.
* PMON will restart death dispatches will are during instance recovery.
3. LGWR ;
Lgwr writes from log Buffer Cache to redo logfiles.
* when commit occurs.
* every 3 seconds.
* when 1 MB of redo is generated.
* when 1/3 full of log Buffer Cache.
* Before DBWR writes.
4. DBWR :
Dbwr writes to Database Buffer Cache to Datafiles.
* when checkpoint occurs.
* when table is droped.
* when tablespace is offline or read only or begin backup mode.
* After log writer writes.
5.CKPT :
* Checkpoint process will update the controlfile and all data files header with the
latest SCN ( System Change Number ).
* Checkpoing process will be initiated by checkpoing event when ever a logswitch occurs
6. ARCHn;
it will generated the ofline archive logs when the database is archive mode.
7. MMON :
it will write the data from sysaux tablespace to AWR Report.
8. MMAN :
it allocate memory to the SGA components.
9. RVWR :
it will writes the Flash logs to FRA Location.
It is a combination of Instance and Database.
What is Instance ?
It is a combination of Memory Structure of SGA and Background processes.
SGA ( Shared Global Area) :
* it is a memory area which can be shared by all the users of database.
* SGA has been build with fllowing components.
1. Shared Pool
This has been divided into subcomponents
i. Library Cache
ii. Data Dictionary Cache
i. Libray Cache:
it contains sharable parsed SQL and PL/SQL Statements.
ii. Data Dictionary Cache:
it contains Dictionary Information and a copy of Base tables,the data will be stored in the form of Rows,it is also called Row Cache.
2. DataBase Buffer Cache:
It Stores a copy of user Data or server process stores data before giving to the user.
LRU LIST :
The Data will be stored in the form of Blocks.
WRITE LIST :
The Modified Blocks become Dirty will be ready to move in data files.
3. Log Buffer Cache:
It Stores Redo Entries,Every single Automatic change happen in database it is called redo entry.
4. Large Pool:
it stores rman backup backup information
5. Java Pool:
it is used for executeing or parsing the java programs.
6. Stream Pool:
it is a Memory Area which will be used when oracle streams is implemented.
PGA ( Private Global Area ):
it is a Memory Area when a user statements will be executed and also sorting the statement will be performed in PGA.
parameter of PGA : PGA_AGGREGATE_TARGET
User Process ?
it is a process which will be created on the client side when ever application is started.
Server Process ?
it is the process reside on server side which will do the work on the half of user process.
What are Oracle Background Processes ?
1. SMON
2. PMON
3. DBWR
4. LGWR
5. CKPT
6. ARCHn
7. MMON
8. MMAN
9. CTWR ........etc
1. SMON :
* SMON will do instance recovery.it will be done in three steps,
a. Write the committed transactions to datafiles
b. Open the DataBase for User Access.
c. Rollback the uncommitted transtractions
* SMON Collase the free space in table space.
* SMON will release the temporary segment onces the transactions is completed.
* SMON will have 16 slave processes.
2. PMON :
* PMON will authenticate the user by using Dictionary Information.
* PMON will register the listener with the instance.
* PMON will release locks and resources when the session is abnormally terminated.
* PMON will restart death dispatches will are during instance recovery.
3. LGWR ;
Lgwr writes from log Buffer Cache to redo logfiles.
* when commit occurs.
* every 3 seconds.
* when 1 MB of redo is generated.
* when 1/3 full of log Buffer Cache.
* Before DBWR writes.
4. DBWR :
Dbwr writes to Database Buffer Cache to Datafiles.
* when checkpoint occurs.
* when table is droped.
* when tablespace is offline or read only or begin backup mode.
* After log writer writes.
5.CKPT :
* Checkpoint process will update the controlfile and all data files header with the
latest SCN ( System Change Number ).
* Checkpoing process will be initiated by checkpoing event when ever a logswitch occurs
6. ARCHn;
it will generated the ofline archive logs when the database is archive mode.
7. MMON :
it will write the data from sysaux tablespace to AWR Report.
8. MMAN :
it allocate memory to the SGA components.
9. RVWR :
it will writes the Flash logs to FRA Location.
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