Automatic Memory Management. AMM manages all SGA + PGA memory together, allowing it to shift memory from SGA to PGAs and vice versa. we need to set a MEMORY_TARGET (and if you like, MEMORY_MAX_TARGET parameter).
in our Instances this parameter set by default as below
show parameter MEMORY_MAX_TARGET ;
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
memory_max_target big integer 0
