MULTIPLE DBWn PARAMETERE DEFINE
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WHEN THE SGA SIZE IS MORE CONSUME AND AT A TIME ONE DBWn PROCESS ,ALL BUFFER CACHE DATA IS
WRITE ON DATAFILE BUT IN CASE YOU WILL EXECUTE SOME QUERIES BUT PROCESS IS NOT ALLOCATED
THE SPACE ON BUFFER CACHE ,SO MULTIPLE DBWn IS WORK FAST TWO OR MORE PROCESS IS WRITE A DATA
ON DATAFILE PARALLELY AND PROCESS ALLOCATE A SPACE ON BUFFER CACHE.
PARAMETER IS DEFINE ON THIS FILE:-
( Oracle I_O Slave Waits dbwr parallel DML )
SHOW PARAMETE DB_WRITER_%
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DBWR_IO_SLAVES
Parameter type Integer
Default value 0
Parameter class Static
Range of values 0 to operating system-dependent
DBWR_IO_SLAVES is relevant only on systems with only one database writer process (DBW0). It specifies the number of I/O server processes used by the DBW0 process. The DBW0 process and its server processes always write to disk. By default, the value is 0 and I/O server processes are not used.
If you set DBWR_IO_SLAVES to a nonzero value, the number of I/O server processes used by the ARCH and LGWR processes is set to 4. However, the number of I/O server processes used by Recovery Manager is set to 4 only if asynchronous I/O is disabled (either your platform does not support asynchronous I/O or disk_asynch_io is set to false.
Typically, I/O server processes are used to simulate asynchronous I/O on platforms that do not support asynchronous I/O or that implement it inefficiently. However, you can use I/O server processes even when asynchronous I/O is being used. In that case the I/O server processes will use asynchronous I/O.
I/O server processes are also useful in database environments with very large I/O throughput, even if asynchronous I/O is enabled.
NOTE:-
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IT MEANS THE "DBWR_IO_SLAVES" INITIAL 2 OR 3 PROCESS ARE EXCUTES PARALLELY
IF THE "DBWR_IO_SLAVES" NOT INITIALIZED THE PROCESS ARE EXECUTED IN A QUEUE
IN THIS WORK ON "DB_WRITER_PROCESS" PARAMETER INITIAL FIRST .
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