Oracle: Monitor Shared Pool and Large Pool Memory

Shared pool and large pool usage should be monitored as trends, not judged from a single “free memory” number. Oracle can use most of a pool efficiently, and a low free value does not by itself prove memory pressure.

Summarize current allocations

SELECT pool,
       name,
       ROUND(SUM(bytes) / 1024 / 1024, 1) AS mb
FROM   v$sgastat
WHERE  pool IN ('shared pool', 'large pool')
GROUP  BY pool, name
ORDER  BY pool, mb DESC;

Check free memory

SELECT pool,
       ROUND(SUM(bytes) / 1024 / 1024, 1) AS free_mb
FROM   v$sgastat
WHERE  pool IN ('shared pool', 'large pool')
AND    name = 'free memory'
GROUP  BY pool
ORDER  BY pool;

Capture these results at regular intervals and correlate changes with workload, parse activity, parallel execution, Recovery Manager operations, and shared server usage.

When ORA-04031 occurs

The error text identifies the requested allocation size, heap, and allocation context. Save the full error, alert-log messages, incident time, and the workload that was running. Then check for:

• Excessive hard parsing or many non-shareable SQL statements
• Application code that generates many nearly identical statements
• Large or fragmented allocations in the named pool
• An undersized manually configured pool, or an automatic-memory configuration that needs review

Do not flush the shared pool or resize memory as a reflex. Those actions can cause a parse storm or hide the evidence. Test changes and use Oracle’s supported memory advisories and diagnostics for the installed release.

Alerting

Alert on repeated allocation failures, sustained adverse trends, and workload symptoms—not on one fixed free-memory threshold. Send query results through your monitoring platform or a supported database alerting mechanism. The former article’s undocumented DBMS_SYSTEM.KSDWRT procedure has been removed.