How to Monitor Oracle Shared Pool Usage with V$SGASTAT

calendar Aug 22, 2025 / · 2 min read · oracle database shared pool memory tuning dba scripts sql query oracle performance database monitoring administration v$sgastat  ·
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How to Monitor Oracle Shared Pool Usage with V$SGASTAT

Database Administrators (DBAs) frequently need to track memory allocation inside Oracle’s SGA (System Global Area), especially within the Shared Pool. Monitoring the shared pool helps identify memory fragmentation, excessive parsing, and potential memory-related performance issues.

One practical way to check shared pool usage is by querying the dynamic performance view V$SGASTAT.

SQL Script to Display Pool Usage

1SELECT name, 
2       SUM(bytes) 
3FROM   v$sgastat 
4WHERE  pool LIKE 'shared pool' 
5GROUP BY name;
6/

Purpose of the Script

  • Monitors shared pool usage: Shows how memory is distributed across different shared pool components.
  • Helps identify fragmentation: By grouping allocations by name, DBAs can see where memory is concentrated.
  • Supports tuning efforts: Knowing which areas consume memory guides parameter tuning (e.g., adjusting SHARED_POOL_SIZE).

Breakdown of the Script

  1. SELECT name, SUM(bytes)
    • name → Represents the memory structure or component inside the shared pool (e.g., SQL area, free memory, library cache).
    • SUM(bytes) → Aggregates the memory allocated to each component.
  2. FROM v$sgastat
    • V$SGASTAT contains statistics about the system global area. It breaks down memory usage by pool, name, and size.
  3. WHERE pool LIKE 'shared pool'
    • Filters results to return only the Shared Pool segment of the SGA.
  4. GROUP BY name
    • Ensures results are reported per component for better readability and analysis.

Key Insights for DBAs

  • Identify “free memory”: If “free memory” is consistently low, the shared pool may be undersized.
  • Check for heavy ‘SQL area’ usage: Excessive memory here may indicate too much parsing or lack of bind variable usage.
  • Library cache pressure: Large allocation for the library cache may require tuning cursor sharing.
  • Helps in proactive monitoring: Reviewing periodically aids in avoiding ORA-4031 “unable to allocate memory” errors.

Practical Use Cases

  • Performance tuning: Quickly see whether SQL parsing or caching consumes most memory.
  • Troubleshooting errors: If ORA-04031 errors occur, this query helps confirm shared pool fragmentation or shortage.
  • Capacity planning: Helps DBAs adjust memory parameters in advance as workload scales.

Conclusion

This script is simple but powerful for Oracle DBAs focused on memory tuning and system stability. By monitoring the shared pool breakdown with V$SGASTAT, administrators can prevent performance degradation and ensure optimal use of Oracle memory resources.

References

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