Setting of db_cache_size seems strange...?

11.2.0.2

Hi,

I got a recommendation from Support to set hard values as we have seen a lot of resize operations.

alter system set memory_target=7G scope=both;

alter system set shared_pool_size=1G scope=both;
alter system set db_cache_size=5000M scope=both;

alter system set db_cache_size = 5000M
alter system set db_cache_size = 5000M
*
ERROR at line 1:
ORA-02097: parameter cannot be modified because specified value is invalid
ORA-00384: Insufficient memory to grow cache

I set it at 3500MB.

sho parameter db_c
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
db_cache_size big integer 16M