Oracle ORA-00371 Error: Causes and Solutions Complete Guide

ORA-00371: Not Enough Shared Pool Memory

ORA-00371 is raised when Oracle's Shared Pool — the SGA region responsible for caching parsed SQL, PL/SQL code, and data dictionary information — runs out of available memory. This error typically surfaces during peak workloads or when the database is heavily hit with hard parsing activity. Left unaddressed, it can cascade into ORA-04031 errors and cause widespread session failures across the entire database.

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Top 3 Causes

1. Undersized SHARED_POOL_SIZE Parameter

The most straightforward cause: the shared pool is simply too small for the workload. As applications grow, the original sizing becomes inadequate. Check current usage before making changes.

-- Check current shared pool allocation and free memory
SELECT name,
       ROUND(bytes / 1024 / 1024, 2) AS size_mb
FROM   v$sgastat
WHERE  pool = 'shared pool'
  AND  name IN ('free memory', 'library cache', 'dictionary cache')
ORDER  BY bytes DESC;

-- Review current parameter settings
SHOW PARAMETER shared_pool_size;
SHOW PARAMETER sga_target;

2. Excessive Hard Parsing Due to Literal SQL

When applications embed literal values directly into SQL instead of using bind variables, Oracle treats each unique statement as a brand-new query and performs a full hard parse every time. This floods the library cache with thousands of unique cursors and drains shared pool memory rapidly.

-- Find top SQL statements causing hard parses
SELECT sql_text,
       parse_calls,
       executions,
       ROUND(parse_calls / DECODE(executions,0,1,executions)*100,2) AS parse_ratio_pct
FROM   v$sql
WHERE  executions > 0
ORDER  BY parse_calls DESC
FETCH  FIRST 10 ROWS ONLY;

-- Identify literal SQL flooding the library cache (same pattern, many cursors)
SELECT SUBSTR(sql_text,1,60) AS sql_sample,
       COUNT(*)              AS cursor_count
FROM   v$sql
GROUP  BY SUBSTR(sql_text,1,60)
HAVING COUNT(*) > 20
ORDER  BY cursor_count DESC;

3. Memory Fragmentation from Large Object Reloading

Large PL/SQL packages and objects require contiguous memory blocks when loaded into the shared pool. If the pool is fragmented, Oracle cannot find a large enough free block even when total free memory appears sufficient. This triggers repeated aging-out and reloading cycles, worsening fragmentation over time.

-- Check for large objects in the library cache
SELECT owner, name, type,
       ROUND(sharable_mem/1024/1024, 2) AS size_mb,
       loads,
       kept
FROM   v$db_object_cache
WHERE  sharable_mem > 1048576   -- objects larger than 1 MB
ORDER  BY sharable_mem DESC
FETCH  FIRST 15 ROWS ONLY;

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Quick Fix Solutions

Increase shared pool size dynamically (no restart needed in most cases):

-- Increase shared pool size on the fly (ASMM environment)
ALTER SYSTEM SET shared_pool_size = 512M SCOPE = BOTH;

-- Increase overall SGA target to give shared pool more room
ALTER SYSTEM SET sga_target = 4G SCOPE = BOTH;

Emergency flush to relieve fragmentation (use with caution in production):

-- Flush the shared pool - causes temporary performance dip
-- Run during a maintenance window only
ALTER SYSTEM FLUSH SHARED_POOL;

Pin large, frequently-used packages to prevent aging-out:

-- Pin critical packages into the shared pool at startup
EXECUTE DBMS_SHARED_POOL.KEEP('OWNER.PACKAGE_NAME', 'P');

-- Verify pinned objects
SELECT owner, name, type, kept
FROM   v$db_object_cache
WHERE  kept = 'YES';

Enable CURSOR_SHARING as a temporary workaround (test before applying):

ALTER SYSTEM SET cursor_sharing = FORCE SCOPE = BOTH;

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Prevention Tips

1. Monitor shared pool utilization proactively.
Schedule a monitoring job that alerts when shared pool usage exceeds 85%. Use v$shared_pool_advice to right-size the pool based on actual workload data.

-- Shared Pool Advisor recommendations
SELECT shared_pool_size_for_estimate AS pool_mb,
       estd_lc_time_saved_factor     AS perf_factor
FROM   v$shared_pool_advice
ORDER  BY shared_pool_size_for_estimate;

2. Enforce bind variable usage from day one.
Mandate bind variables in your development coding standards and include literal SQL detection as part of every code review. Regularly query v$sql in lower environments to catch literal SQL patterns before they reach production. This single practice eliminates the majority of shared pool pressure in OLTP systems.

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Related Errors

• ORA-04031 — Direct "unable to allocate shared memory" failure; often the next error after ORA-00371 appears in alert logs.
• ORA-00604 — Recursive SQL error that frequently wraps ORA-04031 or ORA-00371 in the error stack.

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📖 Want a more detailed guide?
Check out the full in-depth version (Korean) on oraerror.com — includes detailed analysis, additional SQL examples, and prevention tips.