Resetting an Oracle Database Parameter to Its Default Value
Reset or unset a Oracle parameter in the spfile
Setting a parameter to =' ' often isn't enough. Do this instead.. The sid='*' bit is always necessary, even in non RAC database.
SQL Code
1alter system reset <parameter> scope=spfile sid='*'
2/
Sample Oracle Output:
1no rows selected
2SQL>
Purpose:
- To reset a specified database initialization parameter to its default value, ensuring the change takes effect across all instances in a Real Application Clusters (RAC) environment upon the next database startup. This aids in troubleshooting, optimizing performance, or addressing configuration issues.
Breakdown:
- Command:
alter system reset
: Initiates the process of modifying a parameter value. - Parameter:
<parameter>
: Placeholder for the exact parameter to be reset (e.g.,memory_target
,processes
,open_cursors
). - Scope:
scope=spfile
: Specifies that the change should be made to the server parameter file (SPFILE), which persists across database restarts. - SID:
sid='*'
: Applies the change to all instances within a RAC environment, ensuring consistency. - Terminator:
/
: Signals the end of the SQL statement.
Key Points:
- Persistent Change: Modifies the SPFILE, making the reset value permanent.
- RAC-Wide Impact: Affects all instances in a RAC environment, ensuring uniform configuration.
- Effective Upon Restart: Takes effect only after the database is restarted, allowing for controlled implementation.
Insights and Explanations:
- Troubleshooting: Resetting parameters to defaults can help isolate issues caused by incorrect configuration settings.
- Performance Tuning: Adjusting parameters to their optimal values can enhance database performance.
- Security Hardening: Resetting sensitive parameters to secure defaults can mitigate vulnerabilities.
- Caution:
- Exercise careful judgment when resetting parameters, as it can potentially disrupt database operations if not done thoughtfully.
- Consult Oracle documentation and best practices for specific parameter implications and recommended values.
- Consider Database Restart: After execution, a database restart is often necessary for the change to take effect.