SGA memory is private memory segements: PGA memory is shared memory segments.
Session can write to the PGA, not the SGA.
The SGA is written to by all sessions: a PGA is written by one session.
The PGA is allocated at instance startup.
The SGA is allocated at instance startup.
The database buffer cache
The Java Pool
The large pool
The log buffer
The program global area
Server processes use Oracle Net to connect to the instance.
Background processes use Oracle Net to connect to the database.
User processes read from the databae and write to the database.
Server processes execute SQL received from user processes.
To the data block in the cache, and the redo log buffer.
To the data block on disk, and the current online redo log file.
The session writes to the database buffer cache, and the log writer to the current online redo log file.
Nothing the written until the change is committed.
ARCn, the archive process
CKPT, the checkpoint process
DBWn, the database writer
LGWR, the log writer
MMON, the manageability monitor
The CKPT process signals a checkpoint
The DBNw process writes the transaction's changed buffers to the datafiles.
The LGWR flushes the log buffer to the online redo log.
The ARCn process writes the change vectors to the archive redo log.
The archive process
The checkpoint process
The database writer process
The log writer process
The session server process
There must be at least one log file group, with at least one memeber
There must be at least one log file group, with at least two memebers
There must be at least two log file group, with at least one memebers each
There must be at least two log file group, with at least two memebers eacg
In the controlfile
In the current online log file group
In the header of each datafile
In the system global area