Oracle Solution for Error ora-00840

ORA-00840: PGA_AGGREGATE_TARGET cannot be modified to the specified value

What triggered the Error:

The specified value of PGA_AGGREGATE_TARGET was not compatible with current settings of SGA_TARGET and MEMORY_TARGET/MEMORY_MAX_TARGET.

What should we do to fix it:

Set PGA_AGGREGATE_TARGET to be no more than the difference of MEMORY_TARGET/MEMORY_MAX_TARGET and SGA_TARGET.