Oracle Database: Managing PFILE and SPFILE

Oracle databases rely on initialization files to configure instance parameters, ensuring smooth operations and optimal performance. There are two types of initialization files: PFILE (Parameter File) and SPFILE (Server Parameter File). Both serve the same fundamental purpose but differ in functionality, persistence, and management. Understanding the differences between them and how to manage them efficiently can help database administrators optimize database performance.

In this article, we’ll explore PFILE and SPFILE in detail, discussing their key differences, how to create and modify them, best practices, and their role in database management.

Understanding PFILE and SPFILE

1. What is PFILE?

PFILE, or Parameter File, is a text-based file containing initialization parameters for an Oracle database instance. It is manually created and maintained by database administrators.

• PFILE is read during database startup, but Oracle does not track changes made to it during runtime.

• It must be edited manually for changes to take effect.

• Stored under the $ORACLE_HOME/dbs directory with the naming convention init.ora (e.g., initORCL.ora).

• Requires a database restart for any modifications to take effect.

2. What is SPFILE?

SPFILE, or Server Parameter File, is a binary file that provides dynamic management of database parameters. It is the preferred choice over PFILE due to its advanced capabilities.

• SPFILE allows for parameter modifications without restarting the database.

• Changes can be made for the current session or persist across reboots.

• Oracle automatically updates SPFILE when parameters are altered dynamically.

• Stored under $ORACLE_HOME/dbs with the naming convention spfile.ora (e.g., spfileORCL.ora).

  
  

Key Differences: PFILE vs. SPFILE

Feature	PFILE	SPFILE
File Type	Text file (manually editable)	Binary file (Oracle managed)
Parameter Modification	Requires database restart	Can modify dynamically
Persistence	Non-persistent	Persistent across reboots
Dynamic Changes	No	Yes
Creation	Manually created by DBA	Created using Oracle commands

Creating and Managing PFILE and SPFILE

1. Creating an SPFILE from a PFILE

If the database is running using a PFILE, you can create an SPFILE from it with the following command:

CREATE SPFILE FROM PFILE;

This creates an SPFILE in the default location ($ORACLE_HOME/dbs). If you want to specify a custom location:

CREATE SPFILE='/custom/path/spfileORCL.ora' FROM PFILE='/custom/path/initORCL.ora';

2. Creating a PFILE from an SPFILE

To generate a PFILE from an existing SPFILE, use:

CREATE PFILE FROM SPFILE;

For a custom location:

CREATE PFILE='/custom/path/initORCL.ora' FROM SPFILE='/custom/path/spfileORCL.ora';

3. Checking Whether the Database is Using PFILE or SPFILE

Run the following command to check if the database is using an SPFILE:

SHOW PARAMETER spfile;

If an SPFILE is in use, the location will be displayed. If the result is blank, the database is using a PFILE.

Modifying Parameters in SPFILE and PFILE

1. Modifying Parameters in SPFILE

SPFILE allows dynamic changes to parameters, which can be applied in three ways:

• Immediate change (applies until restart):

ALTER SYSTEM SET parameter_name = value SCOPE=MEMORY;

• Permanent change (persists across reboots):

ALTER SYSTEM SET parameter_name = value SCOPE=SPFILE;

• Both immediate and permanent change:

ALTER SYSTEM SET parameter_name = value SCOPE=BOTH;

Example:

ALTER SYSTEM SET sga_target = 1024M SCOPE=BOTH;

2. Modifying Parameters in PFILE

Since PFILE is a text file, you can edit it using any text editor like vi (Linux) or Notepad (Windows). Changes take effect only after a database restart.

Example PFILE (initORCL.ora):

db_name=ORCL

memory_target=1G

control_files=(/u01/app/oracle/oradata/ORCL/control01.ctl, /u01/app/oracle/oradata/ORCL/control02.ctl)

After editing, restart the database:

SHUTDOWN IMMEDIATE;

STARTUP;

Switching Between PFILE and SPFILE

1. Switching from SPFILE to PFILE

To start the database using a PFILE instead of SPFILE:

STARTUP PFILE='/path/to/initORCL.ora';

2. Switching from PFILE to SPFILE

To switch back to SPFILE, create it from the PFILE and restart:

CREATE SPFILE FROM PFILE;

STARTUP;

Oracle will automatically use the SPFILE if it exists in the default location.

Best Practices for Managing PFILE and SPFILE

1. Prefer SPFILE: SPFILE is recommended for production environments as it allows for dynamic parameter changes without restarts.

2. Backup PFILE Regularly: Even if using SPFILE, keeping a backup PFILE can help in case of startup issues.

3. Track Parameter Changes: Maintain a record of all parameter modifications to aid troubleshooting.

4. Test Changes in Non-Production: Before applying changes in production, test them in a staging environment.

5. Use SCOPE=BOTH When Necessary: For critical changes, use SCOPE=BOTH to apply changes immediately and persist them.

Conclusion

Both PFILE and SPFILE play essential roles in Oracle database management. While PFILE is simple and manually controlled, SPFILE offers greater flexibility with dynamic changes. Understanding how to create, modify, and switch between these files ensures a smooth database operation.

By following best practices and using SPFILE for production environments, you can achieve better efficiency and control over Oracle instance configurations.

References

• Oracle Database Documentation

• DBA Best Practices Guide

Disclaimer: This article is for informational purposes only. Always test changes in a controlled environment before applying them to production.