Two Parameter files for Oracle Database Initialization

Two types of Oracle Database initialization parameter files:
File: initsid. ora spfilesid. ora
Path: $ ORACLE_HOME/dbs

Differences between plain text parameter files and binary parameter files:
1. Modify parameters in different ways: When initsid. ora modifies the parameters, directly edit the file and save it. Spfilesid. ora must be changed using the command.
2. Different priorities
3. dynamically store modified Parameters
4. Different locations exist.
The plain text can exist on the client.
Binary files must exist on the server.
5. rman can back up binary parameter files, but cannot back up text parameter files.

The parameter type being used by the verification database:
Select distinct ISSPECIFIED from v $ spparameter;
If the value is true, the binary parameter file is used.
If only false is used, it is the pure parameter file [LINUX community www.LinuxIDC.com]

SQL> select ISSPECIFIED, count (*) from v $ spparameter group by ISSPECIFIED;

Isspec count (*)
----------------
TRUE 23
FALSE 237
The preceding query indicates that there are 23 parameters and binary parameter files. The default value is 237.

Interchange of two types of parameter files:
SQL> create pfile from spfile;
SQL> create spfile from pfile;
The above command can be used in the connected sys without starting the database.

Parameter file priority:
Spfilesid. ora
Spfile. ora
Initsid. ora

Query the parameter settings of the binary parameter file:
SQL> select name, value from v $ spparameter where ISSPECIFIED = 'true ';

There are three options to modify parameters:
SQL> show parameter pga_aggregate_target;

NAME TYPE VALUE
-----------------------------------------------------------------------------
Pga_aggregate_target big integer 77 M

SQL> alter system set pga_aggregate_target = 80 m scope = memory;
System altered.
Only modify the memory value, without changing the parameter file settings. The value of the database is still old when the database is started again next time. The premise is that the parameter can be modified dynamically, for static parameters, you can only use the following method.

SQL> alter system set pga_aggregate_target = 85 m scope = spfile;
System altered.
Only binary files are modified, but the memory is not modified. static parameters can only be changed first and then the database is restarted.

SQL> alter system set pga_aggregate_target = 78 m scope = both;
System altered.
Modify the binary file and memory simultaneously. This parameter must be dynamically changeable.

SQL> alter system set pga_aggregate_target = 77 m;
System altered.
If no modification is specified, the parameter file and memory are modified at the same time by default. The default value is both.