Eliminating High CPU Spikes in Ellucian Banner Student Registration (Oracle DB 19c)

Symptom & Diagnostic Logs

During high-concurrency registration windows, database CPU utilization hits 100%. Active Session History (ASH) highlights top SQL ID 7f3k8m9pq2z1a targeting table SATURN.SFRSTCR.

Application logs report:

ORA-01555: snapshot too old: rollback segment number 102 with name "_SYSSMU102_18294819$" too small
Top Wait Event: db file sequential read (98% DB time)

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Root Cause Analysis

The Oracle Cost-Based Optimizer (CBO) switches from an indexed access path (SFRSTCR_KEY_INDEX) to a parallel full table scan on SFRSTCR when stale table statistics cause the cardinality estimate to drop below 10 rows.

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Step-by-Step Resolution Runbook

Step 1: Lock & Update Table Statistics

Run the following PL/SQL block during off-peak hours to update table and column histograms accurately:

BEGIN
  DBMS_STATS.GATHER_TABLE_STATS(
    ownname          => 'SATURN',
    tabname          => 'SFRSTCR',
    estimate_percent => DBMS_STATS.AUTO_SAMPLE_SIZE,
    method_opt       => 'FOR ALL COLUMNS SIZE AUTO',
    degree           => 4,
    cascade          => TRUE
  );
END;
/

Step 2: Create SQL Plan Baseline

Capture the optimal execution plan and prevent future plan regressions:

DECLARE
  l_plans_loaded PLS_INTEGER;
BEGIN
  l_plans_loaded := DBMS_SPM.LOAD_PLANS_FROM_CURSOR_CACHE(
    sql_id          => '7f3k8m9pq2z1a',
    plan_hash_value => 3819204912,
    fixed           => 'YES'
  );
END;
/

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Diagnostic Bundle Collection

Sanitize your AWR/ADDM diagnostic traces locally before submitting for review:

node ./scripts/collector/dbpros-sanitize-collect.js --input-log /u01/app/oracle/diag/rdbms/banner/banner_ora_40192.trc

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