Purge Historical Bind Variable Information in Oracle 19c

Описание: Learn how to effectively delete historical bind variable information from Oracle 19c using `FLUSH` commands and `DBMS_WORKLOAD_REPOSITORY`. Ensure optimal database performance while managing sensitive data.
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How to Purge Historical Bind Variable Information from Oracle Database 19c

Working with Oracle databases often involves managing a significant amount of data efficiently. One crucial aspect is ensuring that historical bind variable information does not compromise performance or security. In this guide, we’ll explore how to purge this information, allowing you to maintain your database effectively.

Understanding Bind Variables in Oracle

Bind variables are placeholders used in SQL statements. They help optimize performance, particularly in the context of repeated SQL executions, by allowing Oracle to reuse execution plans and reduce parsing times. However, over time, especially in production environments, bind variable data might accumulate, raising the question: How do you purge this historical information?

The Need for Purging Bind Variables

In certain situations, you might need to purge historical bind variable information due to:

Security Concerns: Sensitive data such as passwords may reside within these bind variables.

Performance Issues: Excessive historical data in the memory can slow down database operations.

Methods for Purging Bind Variables

There are two main methods to purge bind variables: removing from memory and removing from disk.

1. Remove Bind Variables from Memory

The command ALTER SYSTEM FLUSH SHARED_POOL is used to clear SQL bind data from memory. However, remember that this can lead to temporary performance problems, as the database may need some time to rebuild performance metadata.

Steps to Remove from Memory

Check the number of rows currently in memory:

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Execute the flush command:

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Verify the number of rows post-flush:

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Important Note: Running this command on a production database requires caution due to potential performance issues.

2. Remove Bind Variables from Disk

To permanently remove SQL statement metadata and historical bind variable data from the Automatic Workload Repository (AWR), the DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE procedure is used.

Steps to Remove from Disk

Check the existing snapshot counts:

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Execute the PL/SQL block to drop snapshots:

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Check the count of rows after snapshots have been dropped:

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Conclusion

While purging historical bind variable information is vital for security and performance, it's essential to proceed with caution. Flushing the shared pool removes data from memory but does not touch historical records on disk, while dropping snapshots can erase a significant amount of performance data. Unless necessary, allowing information to age out gracefully is often the best approach.

Being proactive in managing your Oracle database ensures optimal performance and security. Keep these commands in mind as you navigate your database management tasks!