1.
SGA & PGA
a. SGA: Shared Area for all the processes/threads
b. PGA: The area for a single process/thread
SGA ∩ PGA == Ø
2.
UGA: The area for the user
a. UGA ⊆ SGA if "Shared Server" is used.
b. UGA ⊆ PGA if "Dedicated Server" is used.
3.Important components of SGA
a.
Redo Buffer — extremely helpful for big/long transactions, since the redo log is involved for transactions.
b.
Block Buffer Cache — Caching query results
c.
Shared Pool —
i. Bascially for compiled SQLs. So, always use "Bind variables" in SQLs because this way there will be too much SQLs in this pool(Think otherwise).
ii.LRU-Cache
d.
Large Pool — For large memory alloacation
4.
SQLs for SGA
a. See pools
select * from V$SGASTAT
b. See pool size
select sum(bytes)/1024/1024 mbytes from V$SGASTAT where pool = ‘shared pool’