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:

1
2no rows selected
3SQL>

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.

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