Hi McDonald,

Thanks for reply.

But, my question still remains. Whether Oracle automatically tune SGA/PGA as per the Memory_max_target if it's needed to exceed from memory_target or not?

If Memory_max_target is 30G and Memory_target is 20G, if needed, will oracle go beyond 20G upto 30G by it's on or DBA have to increase memory by using "alter system set memory_target=30G"

so that means, if it's needed, say 25G, only DBA can increase it. until that oracle will use pre specified 20G only. Right?

In my experience, on most platforms, at amount of memory specified by "memory_max_target" becomes either locked down to only be accessible by Oracle, or is allocated by the OS anyway, so it is rare to see them differing in value. After all, if mem_tgt is 20G and mem_max is 30G, I struggle to see why I would "keep in reserve" that 10G..I may as well use it. 

memory between memory_target and memory_max_target will be reserved in the paging area but never paged in as long as it is not used by oracle processes. we can move memory between instances that way without restart, .e.g.

before: real memory 10G, instance 1: memory_target 5G, memory_max_target 7G, instance 2: memory_target 5G, memory_max_target 7G
after: real memory 10G, instance 1: memory_target 7G, memory_max_target 7G, instance 2: memory_target 3G, memory_max_target 7G

Good evening everyone, our developer has changed the parameters of MEMORY_TARGET and MEMORY_MAX_TARGET in order to increase the execution speed of our oracle database by passing the values to 8G, but after verification we have:
NAME TYPE VALUE
------------------------------------ -------------- ---------------------------
sga_target big integer 7808M
SQL> show parameter sga_max_size;

NAME TYPE VALUE
------------------------------------ -------------- ---------------------------
sga_max_size big integer 7808M
SQL> show parameter pga_aggregate_target;

NAME TYPE VALUE
------------------------------------ -------------- ---------------------------
pga_aggregate_target big integer 2600M
SQL> show parameter pga_aggregate_limit;

NAME TYPE VALUE
------------------------------------ -------------- ---------------------------
pga_aggregate_limit big integer 5200M
SQL> Show parameter memory_target;

NAME TYPE VALUE
------------------------------------ -------------- ---------------------------
memory_target big integer 0
SQL> show parameter memory_max_target;

NAME TYPE VALUE
------------------------------------ -------------- ---------------------------
memory_max_target big integer 0
SQL>
My question is whether the values obtained are normal because after restarting the server the BD no longer runs but as it is a VM under hyper-V I restored from a checkpoint and everything has started again but I'm afraid to restart the server to avoid crashing again.