ORA-02096: specified initialization parameter is not modifiable with this option
The value of fixed_date can only be changed for the entire system (alter system), not for a session. Hence, the following alter session statement causes an ORA-02096: specified initialization parameter is not modifiable with this option error:
alter session set fixed_date = '2021-03-05 18:27:03';
Some parameters cannot be modified in memory, for example the process value, hence the following statement also causes this error:
alter system set processes = 300;
Such parameters must be changed by indicating the scope = spfile clause:
alter system set processes = 300 scope = spfile;
See also
The values of the columns isses_modifiable, issys_modifiable, ispdb_modifiable and isinstance_modifiable of the view v$parameter.