Switching DB to use Automatic Memory Management

1)Check the current values configured for SGA_TARGET and PGA_AGGREGATE_TARGET.

SQL>SHOW PARAMETER TARGET
NAME TYPE VALUE
------------------------------ ----------- ----------------
archive_lag_target integer 0
db_flashback_retention_target integer 1440
fast_start_io_target integer 0
fast_start_mttr_target integer 0
memory_max_target big integer 0
memory_target big integer 0
pga_aggregate_target big integer 200M
sga_target big integer 500M

Add the values of pga_aggregate_target and sga_target. In our case:

PGA_AGGREGATE_TARGET (200M) + SGA_TARGET (500M) =700 M

2)Decide on a maximum amount of memory that you would want to allocate to the database which will determine the maximum value for the sum of the SGA and instance PGA sizes. In our case we decide to set to 808M

3) Change the parameter in initialization parameter file.

Using Spfile
========

SQL>ALTER SYSTEM SET MEMORY_MAX_TARGET = 808M SCOPE = SPFILE;
SQL>ALTER SYSTEM SET MEMORY_TARGET = 808M SCOPE = SPFILE;
SQL>ALTER SYSTEM SET SGA_TARGET =0 SCOPE = SPFILE;
SQL>ALTER SYSTEM SET PGA_AGGREGATE_TARGET = 0 SCOPE = SPFILE;