ORA-04031: Unable to Allocate Bytes of Shared Memory – Complete Oracle DBA Troubleshooting Guide

Oracle ORA-04031 shared memory troubleshooting guide

The ORA-04031: unable to allocate bytes of shared memory error occurs when Oracle Database cannot satisfy a shared-memory allocation request from the relevant SGA memory component. The affected area may include the Shared Pool, Large Pool, Java Pool, or another SGA-related memory area.

ORA-04031 is a diagnostic symptom rather than a single root cause. It can be associated with insufficient memory sizing, memory pressure, allocation behavior, excessive hard parsing, application SQL that generates many distinct cursors, large memory consumers, automatic memory-management configuration, or an Oracle software defect.

The complete ORA-04031 message contains valuable information about the affected memory area and allocation request. For this reason, DBAs should identify the failed allocation and investigate the underlying cause before changing memory parameters.

This comprehensive Oracle DBA guide explains the ORA-04031 error, Oracle SGA memory architecture, common causes, diagnostic SQL, Alert Log and trace-file analysis, Shared Pool investigation, AWR and ASH considerations, RAC and Data Guard considerations, OCI considerations, remediation strategies, prevention techniques, and production DBA best practices.

Quick Diagnosis

Capture the complete ORA-04031 error message.
Identify the affected memory pool or heap.
Review the Oracle Alert Log and related trace information.
Check SGA and relevant pool configuration.
Investigate memory pressure, allocation behavior, SQL parsing, and workload changes.
Correct the underlying cause.
Resize the affected memory component only when diagnostics justify the change.

Do not treat ORA-04031 as proof that the server simply needs more RAM. The correct solution depends on the affected memory area and the evidence collected during diagnosis.

Error Message

ORA-04031: unable to allocate 4096 bytes of shared memory
("shared pool","unknown object","SQLA","kglsim object batch")

The exact message varies according to the Oracle component requesting memory and the memory area involved.

For example:

ORA-04031: unable to allocate 8192 bytes of shared memory
("large pool","session heap","PX","parallel execution")

Another possible example is:

ORA-04031: unable to allocate 16384 bytes of shared memory
("java pool","Java Heap","JVM","class loading")

The information inside the parentheses is particularly useful because it can help identify the affected memory area, allocation type, and Oracle component involved.

Understanding the ORA-04031 Error Message

The ORA-04031 message contains diagnostic information that can help narrow the investigation.

Message Component	Meaning
4096 Bytes	The amount of memory Oracle attempted to allocate in this example.
Shared Pool	The memory component associated with the failed allocation.
Unknown Object	The allocation context or object identified by Oracle.
SQLA	An Oracle internal allocation component.
kglsim object batch	Additional internal information describing the allocation request.

The exact interpretation of the allocation context depends on the Oracle release and workload. The complete error message should therefore be preserved when investigating the incident.

What Is ORA-04031?

ORA-04031 occurs when Oracle cannot satisfy a shared-memory allocation request from the relevant SGA memory component.

Possible contributing conditions include:

Insufficient sizing of the affected memory component.
Memory pressure caused by workload requirements.
Allocation and memory-usage patterns within the affected pool.
Excessive hard parsing or large numbers of distinct SQL statements.
Applications that generate excessive numbers of cursors or SQL variants.
Large PL/SQL or other memory-consuming objects.
Automatic memory-management configuration issues.
Memory growth caused by an application or Oracle component.
Oracle software defects or known bugs.

Memory fragmentation or allocation behavior can contribute to allocation failures, but it should not automatically be assumed to be the root cause of every ORA-04031 incident.

Oracle Memory Architecture

Before troubleshooting ORA-04031, it is important to understand the basic Oracle memory architecture.

                 Oracle Instance
                       |
                       v
              System Global Area
                       |
        +--------------+--------------+
        |              |              |
   Shared Pool     Large Pool      Java Pool
        |
   Library Cache
   Dictionary Cache
   SQL Areas
   Other Shared Memory
                       |
                       v
              Database Processes
                       |
                       v
              Process / PGA Memory

Oracle broadly uses two major memory areas:

System Global Area (SGA) – Shared memory associated with the Oracle instance.
Program Global Area (PGA) – Private memory associated with individual server processes.

ORA-04031 is primarily associated with shared-memory allocation within the SGA and its associated memory components.

Major SGA Memory Components

1. Shared Pool

The Shared Pool contains structures associated with SQL and PL/SQL processing, the Library Cache, data dictionary information, and other shared memory structures.

The Shared Pool is one of the memory areas most commonly associated with ORA-04031.

2. Large Pool

The Large Pool can be used for features such as RMAN, shared server, and parallel execution. Depending on configuration and workload, some allocations may otherwise be serviced from the Shared Pool.

An ORA-04031 message identifying the Large Pool should therefore lead to investigation of the workload using that area rather than automatically increasing the Shared Pool.

3. Java Pool

The Java Pool provides memory for Oracle JVM-related functionality and Java stored procedures.

Databases using Oracle JVM components may encounter memory allocation problems involving this area.

4. Streams Pool and Replication-Related Workloads

The Streams Pool is associated with Oracle Streams and certain replication-related components. Depending on the Oracle release and configuration, XStream and integrated capture/apply workloads may also have memory requirements associated with this area.

Always identify the exact memory component named in the ORA-04031 message before deciding which parameter should be investigated.

5. Result Cache and Other SGA Structures

Oracle also manages other memory structures within the SGA. A memory allocation failure should therefore be interpreted using the complete error message, database configuration, and diagnostic information rather than assuming that the Shared Pool is always responsible.

Automatic Memory Management (AMM) vs. Automatic Shared Memory Management (ASMM)

Feature	AMM	ASMM
Primary Scope	SGA and PGA	SGA components
Main Parameter	MEMORY_TARGET	SGA_TARGET
Automatic SGA Resizing	Yes	Yes
PGA Management	Included in overall memory management	Managed separately using PGA parameters
Deployment Consideration	Evaluate platform and operating-system implications	Common approach for automatically managing SGA components

Oracle supports multiple memory-management approaches. The appropriate configuration depends on the Oracle release, operating system, deployment architecture, workload, and operational requirements.

On Linux production systems, DBAs should carefully evaluate the implications of AMM, including shared-memory and large-page configuration, before using MEMORY_TARGET.

Do not recommend AMM or ASMM universally. Validate the current configuration and platform requirements before making memory-management changes.

Common Causes of ORA-04031

1. Insufficient Memory in the Affected Component

The memory component may not be appropriately sized for the workload. The correct response depends on identifying the affected component and confirming the memory requirement.

2. Memory Pressure

A workload change can increase memory requirements and cause allocations to fail even when the previous configuration had been stable.

3. Excessive Hard Parsing

Applications that generate large numbers of distinct SQL statements can increase Library Cache activity and Shared Pool consumption.

4. Excessive Use of Literal SQL

Applications that continuously generate SQL statements containing different literal values can increase the number of distinct SQL statements that Oracle must manage.

5. Large PL/SQL or Shared Objects

Large PL/SQL packages and other shared-memory consumers can increase memory requirements in the relevant SGA component.

6. Memory Growth or Leaks

A component, workload, or Oracle defect may cause memory usage to grow unexpectedly over time.

7. RMAN or Parallel Execution Workloads

Large Pool or related shared-memory requirements may increase during RMAN, shared-server, or parallel-execution activity.

8. Incorrect Memory Configuration

Inappropriate values for parameters such as SGA_TARGET, SGA_MAX_SIZE, SHARED_POOL_SIZE, LARGE_POOL_SIZE, or MEMORY_TARGET may contribute to memory allocation problems.

Common Symptoms

Applications report ORA-04031 errors.
SQL parsing or cursor-related operations fail.
Application sessions experience errors or degraded performance.
RMAN or parallel-execution operations may fail when the affected memory area is involved.
Oracle monitoring tools may report memory pressure.
Library Cache activity may show abnormal behavior.
Memory-related alerts may appear around the same time as the incident.

ORA-04031 Compared With Related Oracle Errors

Error	Description	Main Area
ORA-04031	Unable to allocate shared memory.	SGA / Shared Memory
ORA-04030	Out of process memory when trying to allocate bytes.	Process / PGA Memory
ORA-27101	Shared Memory Realm Does Not Exist.	Instance Startup / Shared Memory
ORA-01034	ORACLE Not Available.	Database Availability
ORA-00600	Internal Oracle Error.	Oracle Kernel / Internal Error

Production DBA Recommendation

Do not increase memory parameters simply because ORA-04031 occurred. First identify the affected pool, review the Alert Log and trace information, inspect memory statistics, and determine whether workload, SQL parsing, configuration, or an Oracle defect is responsible.

Prerequisites Before Troubleshooting

Access to the Oracle Alert Log and ADR.
Access to relevant trace files.
Appropriate database diagnostic privileges.
AWR/ASH access where available and appropriately licensed.
Change-management approval before modifying production memory parameters.
A rollback/change plan for production configuration changes.
A baseline of current memory configuration before making changes.

Step-by-Step Troubleshooting ORA-04031

Successfully resolving ORA-04031 requires identifying which memory area failed and determining why Oracle could not satisfy the allocation request.

Step 1 – Capture the Complete ORA-04031 Message

Record the complete error text, including the memory allocation size and the information contained inside the parentheses.

This information can significantly narrow the diagnostic scope.

Step 2 – Review the Oracle Alert Log

The Oracle Alert Log should be one of the first diagnostic sources reviewed.

Typical diagnostic location:

$ORACLE_BASE/diag/rdbms/<db_name>/<instance>/trace/
alert_<SID>.log

Depending on the Oracle version and environment, use ADR tools such as adrci to locate and inspect diagnostic files.

Look for:

ORA-04031 occurrences.
ORA-00600 or ORA-07445 messages.
ORA-04030 memory errors.
SGA resize operations.
Memory-management messages.
Messages immediately before and after the ORA-04031 event.

DBA Tip

Do not make memory changes before reviewing the diagnostic evidence surrounding the ORA-04031 event.

Step 3 – Review Trace Files

Review the trace files associated with the incident.

Investigate information such as:

Memory allocation requests.
Allocation context.
Heap information.
Shared Pool or other SGA statistics.
Internal Oracle errors.
Evidence of abnormal memory growth.

Step 4 – Identify the Affected Memory Pool

Memory Area	Examples of Workloads / Uses
Shared Pool	SQL processing, Library Cache, PL/SQL, dictionary-related shared structures
Large Pool	RMAN, shared server, parallel execution and related allocations
Java Pool	Oracle JVM and Java-related functionality
Streams Pool	Oracle Streams and certain replication-related components

The exact memory area named in the error should drive the rest of the investigation.

Step 5 – Review SGA Configuration

SHOW SGA;

SHOW PARAMETER sga_target;

SHOW PARAMETER sga_max_size;

SHOW PARAMETER memory_target;

SHOW PARAMETER memory_max_target;

Review the values in the context of the server's available memory, workload, Oracle architecture, and current memory-management configuration.

Step 6 – Review Shared Pool Configuration

SHOW PARAMETER shared_pool_size;

Then review SGA statistics:

SELECT
    POOL,
    NAME,
    BYTES
FROM V$SGASTAT
ORDER BY POOL, BYTES DESC;

Look for unusually high consumers and changes in memory usage that correspond with the incident.

Step 7 – Review Shared Pool Reserved Statistics

SELECT
    REQUEST_FAILURES,
    LAST_FAILURE_SIZE,
    FREE_SPACE
FROM V$SHARED_POOL_RESERVED;

These statistics can provide useful evidence when investigating large allocation requests in the Shared Pool.

Step 8 – Review Library Cache Activity

SELECT
    NAMESPACE,
    PINS,
    RELOADS,
    INVALIDATIONS
FROM V$LIBRARYCACHE;

Review reloads, invalidations, and other Library Cache statistics together with the workload and incident timeline. High values do not automatically prove that Shared Pool sizing is the root cause.

Step 9 – Investigate Parsing Activity

SELECT
    NAME,
    VALUE
FROM V$SYSSTAT
WHERE NAME LIKE '%parse%';

Investigate whether the workload is generating unusually high parsing activity or large numbers of distinct SQL statements.

Step 10 – Investigate Literal SQL and Cursor Behavior

Applications that generate many SQL statements differing only in literal values may increase parsing activity and Shared Pool pressure.

Example:

SELECT *
FROM employees
WHERE employee_id = 100;

A bind-aware form can allow the application to reuse SQL more effectively where appropriate:

SELECT *
FROM employees
WHERE employee_id = :emp_id;

The application should use an appropriate cursor and bind-variable strategy rather than relying on a single database parameter as a universal fix.

Step 11 – Review AWR Information

Where AWR is available, review the period surrounding the ORA-04031 incident.

Useful areas include:

SQL parsing activity.
Top SQL statements.
Database workload changes.
SGA resize operations.
Memory-related statistics.
Relevant wait events.
Changes in workload before the incident.

AWR is an investigative tool. Use its information together with Alert Log, trace, SQL, and memory evidence rather than assuming that AWR alone identifies the root cause.

Step 12 – Review ASH Information

Where available, ASH can help investigate active sessions and workload behavior around the incident.

Consider:

Parsing sessions.
High-load SQL statements.
Relevant wait events.
Changes in application workload.
Sessions active during the ORA-04031 event.

Step 13 – Review Memory Advisors

SELECT *
FROM V$SGA_TARGET_ADVICE;

Memory-advisor information can help evaluate whether changing the SGA target may affect database performance. Treat advisor output as evidence rather than an automatic recommendation.

Step 14 – Resize the Affected Memory Component Only If Justified

If diagnostics demonstrate that the relevant memory component is undersized, a controlled configuration change may be appropriate.

Example only:

-- Example only.
-- Do not use 2G as a universal recommendation.

ALTER SYSTEM
SET shared_pool_size = 2G
SCOPE=BOTH;

Important

The value shown above is only an example. The correct value depends on the Oracle release, current configuration, workload, available server memory, memory-management method, and diagnostic evidence.

Step 15 – Flush the Shared Pool Only as a Controlled Temporary Measure

Flushing the Shared Pool may temporarily change allocation behavior, but it should not be considered a permanent ORA-04031 solution.

ALTER SYSTEM FLUSH SHARED_POOL;

Use this command cautiously in production because it can remove cached SQL and other shared objects, potentially causing additional parsing and performance impact.

Step 16 – Investigate Oracle Software Defects

If the evidence does not support insufficient memory or application behavior, investigate Oracle bugs and known issues for the exact Oracle release and patch level.

Review the relevant Oracle Release Update level, diagnostic trace information, and known Oracle Support documentation before concluding that the database requires additional memory.

Step 17 – Oracle RAC Considerations

In Oracle RAC, each instance has its own SGA. Therefore, ORA-04031 may affect one instance while other instances continue operating normally.

Useful checks include:

srvctl status database

crsctl stat res -t

Compare memory configuration and workload across affected and unaffected RAC instances.

Step 18 – Oracle Data Guard Considerations

Data Guard environments may have different workloads between primary and standby databases. Redo Apply and other Data Guard-related processes can affect memory requirements.

Investigate:

Redo Apply activity.
MRP status.
Redo volume changes.
Standby workload.
Memory configuration on the affected database.

Step 19 – Oracle Cloud Infrastructure (OCI) Considerations

For databases running on OCI, also evaluate the infrastructure layer.

Compute shape memory capacity.
Operating-system memory utilization.
Swap configuration and usage.
Database memory configuration.
Exadata infrastructure, where applicable.
Changes in workload or resource allocation.

Root Cause → Evidence → Action

Possible Root Cause	Evidence to Investigate	Typical Action
Insufficient memory in affected component	Memory statistics, configuration and workload demonstrate sustained pressure	Resize the appropriate component based on evidence
Excessive parsing	Parsing statistics and SQL workload show unusually high parsing activity	Investigate application SQL and cursor strategy
Large memory allocation	ORA-04031 message identifies large allocation request	Investigate affected pool and memory consumers
Workload change	Memory usage increases at a specific business or batch period	Correlate workload with memory requirements
Memory-management configuration	AMM/ASMM parameters do not align with platform/workload requirements	Review configuration and Oracle documentation
Oracle software defect	Trace evidence, memory growth pattern or known Oracle bug	Review Oracle Support and applicable Release Updates

Do Not Do This: Common Emergency Mistakes

Do not repeatedly flush the Shared Pool as the permanent solution.
Do not arbitrarily increase SHARED_POOL_SIZE.
Do not restart the database and assume the problem is permanently fixed.
Do not change multiple memory parameters simultaneously without capturing a baseline.
Do not assume every ORA-04031 is caused by fragmentation.
Do not assume every ORA-04031 is caused by insufficient RAM.
Do not disable automatic memory management without understanding the platform and workload.
Do not make production memory changes without appropriate change control.

Representative Production Scenario

An Oracle E-Business Suite production database began reporting intermittent ORA-04031 errors during business hours. Users experienced application errors and degraded response times.

The investigation began with the Alert Log and diagnostic information. The affected allocation was associated with the Shared Pool. Workload analysis then showed unusually high parsing activity and a large number of distinct SQL statements generated by the application.

The DBA reviewed the application SQL, memory configuration, and workload before making controlled memory changes. Application SQL was subsequently optimized, and memory sizing was adjusted where justified by the workload.

The important lesson is that increasing memory alone should not be considered the complete solution. The DBA must establish the relationship between the failed allocation, workload behavior, memory configuration, and application activity.

Production DBA Troubleshooting Checklist

Verification	Status
Complete ORA-04031 message captured	☐
Alert Log reviewed	☐
Trace files reviewed	☐
Affected memory pool identified	☐
SGA configuration reviewed	☐
Relevant pool utilization checked	☐
Shared Pool statistics reviewed where applicable	☐
Library Cache activity reviewed	☐
Parsing activity analyzed	☐
AWR/ASH reviewed where available	☐
Memory advisor information reviewed	☐
RAC/Data Guard/OCI environment checked if applicable	☐
Oracle patch level reviewed	☐
Root cause identified	☐
Corrective action verified	☐

Oracle Version Considerations

ORA-04031 exists across multiple Oracle Database releases, but memory-management behavior and architecture have evolved over time.

Oracle Version	DBA Considerations
Oracle 11g	Review ASMM/AMM configuration, Shared Pool behavior, and workload characteristics.
Oracle 12c	Consider CDB/PDB architecture and the memory requirements of the multitenant environment.
Oracle 18c / 19c	Use memory advisors, AWR/ASH and diagnostic information to investigate workload and memory behavior.
Oracle 21c	Consider the current memory architecture, multitenant configuration, and release-specific documentation.
Oracle Database 23ai	Validate memory-management behavior and configuration against the current release documentation and deployment model.

Always verify release-specific behavior before applying a memory-management recommendation to a production database.

Automatic Memory Management Best Practices

Understand whether the database uses AMM, ASMM, or manually configured SGA components.
Evaluate the configuration according to the operating system and deployment architecture.
Monitor SGA and PGA usage.
Use memory advisors where appropriate.
Maintain sufficient operating-system memory headroom.
Do not oversize the SGA at the expense of operating-system resources.
Document production memory changes.

Useful Diagnostic SQL Queries

Display SGA Information

SHOW SGA;

Display Memory Parameters

SHOW PARAMETER memory;

SHOW PARAMETER sga;

SHOW PARAMETER shared_pool;

Display SGA Statistics

SELECT
    POOL,
    NAME,
    BYTES
FROM V$SGASTAT
ORDER BY POOL, BYTES DESC;

Display Shared Pool Reserved Statistics

SELECT
    REQUEST_FAILURES,
    LAST_FAILURE_SIZE,
    FREE_SPACE
FROM V$SHARED_POOL_RESERVED;

Display Library Cache Statistics

SELECT
    NAMESPACE,
    PINS,
    RELOADS,
    INVALIDATIONS
FROM V$LIBRARYCACHE;

Display SGA Target Advice

SELECT *
FROM V$SGA_TARGET_ADVICE;

Useful Oracle DBA Commands

Command	Purpose
`SHOW SGA;`	Display SGA information.
`SHOW PARAMETER memory;`	Display memory-related parameters.
`adrci`	Access the Automatic Diagnostic Repository.
`tail -100 alert.log`	Review recent Alert Log entries on Linux systems when the file path is known.
`srvctl status database`	Check Oracle RAC database status.
`crsctl stat res -t`	Display Clusterware resources.

ORA-04031 Troubleshooting Workflow

ORA-04031
      |
      v
Capture Complete Error
      |
      v
Review Alert Log
      |
      v
Review Trace Files
      |
      v
Identify Affected Memory Area
      |
      v
Check SGA / Pool Configuration
      |
      v
Review Memory Statistics
      |
      v
Review SQL / Parsing Activity
      |
      v
Review AWR / ASH
      |
      v
Investigate Workload Changes
      |
      v
Investigate Oracle Bugs if Necessary
      |
      v
Correct Root Cause
      |
      v
Resize Memory Only If Justified
      |
      v
Verify and Monitor

Verification After the Fix

A memory change should not be considered successful simply because the ORA-04031 message disappears immediately.

After implementing corrective action, verify:

ORA-04031 no longer occurs.
The affected memory component remains stable.
Application errors have stopped.
Parsing activity has improved where applicable.
Database performance has returned to an acceptable baseline.
No new memory pressure has appeared elsewhere.
RAC instances remain healthy where applicable.
Backup, batch, and application workloads complete normally.

Frequently Asked Questions (FAQ)

What causes ORA-04031?

ORA-04031 occurs when Oracle cannot satisfy a shared-memory allocation request. Possible causes include insufficient memory in the affected component, workload-related memory pressure, allocation behavior, excessive parsing, application SQL characteristics, configuration issues, or an Oracle software defect.

Does restarting the database fix ORA-04031?

A restart can temporarily clear the current memory state, but it does not necessarily resolve the underlying cause. If the workload, configuration, application behavior, or Oracle defect remains unchanged, the problem can recur.

How do bind variables help?

Bind variables can reduce the number of distinct SQL statements generated by applications and can improve cursor reuse when used appropriately. They should be evaluated as part of the application SQL strategy rather than treated as a universal ORA-04031 fix.

Can ORA-04031 occur when the server still has free RAM?

Yes. Available operating-system RAM does not automatically mean that Oracle can satisfy every individual allocation request within the affected database memory component. The Oracle memory configuration, allocation behavior, workload, and specific error context must be investigated.

Should I always increase SHARED_POOL_SIZE?

No. First identify the affected memory area and establish the root cause. Increasing SHARED_POOL_SIZE is appropriate only when diagnostics indicate that additional Shared Pool capacity is justified.

Can Oracle RAC experience ORA-04031?

Yes. Each RAC instance has its own SGA, so an ORA-04031 condition may affect one instance while other instances remain healthy.

Is ORA-04031 always caused by memory fragmentation?

No. Fragmentation or allocation behavior can contribute to the problem, but ORA-04031 can also result from insufficient pool sizing, workload changes, excessive parsing, large allocations, configuration issues, or Oracle software defects.

About the Author

Rana Abdul Wahid is an Oracle Database Consultant with more than 15 years of experience in Oracle Database Administration, Oracle RAC, Oracle Data Guard, RMAN Backup & Recovery, Oracle E-Business Suite, Oracle Cloud Infrastructure (OCI), Performance Tuning, Linux/Unix Administration, MySQL, Microsoft SQL Server, PostgreSQL, and enterprise database management.

Through this blog, he shares practical Oracle DBA solutions, real-world troubleshooting guides, backup and recovery strategies, Oracle performance-tuning techniques, and enterprise database administration best practices.

Learn more about the author →

Conclusion

The ORA-04031: Unable to Allocate Bytes of Shared Memory error indicates that Oracle cannot satisfy a shared-memory allocation request from the relevant SGA memory component. The error can be associated with insufficient memory sizing, workload-related memory pressure, allocation behavior, excessive parsing, application SQL characteristics, configuration issues, or Oracle software defects.

The correct solution is therefore not simply to increase memory. A structured investigation should begin with the complete ORA-04031 message, followed by review of the Alert Log, trace files, SGA configuration, relevant memory statistics, SQL and parsing activity, and workload changes.

Where available, AWR and ASH can provide additional information about database workload and session activity around the incident. For RAC, Data Guard, and OCI environments, the investigation should also consider the architecture and workload of the affected deployment.

By identifying the affected memory area and addressing the underlying cause before making configuration changes, Oracle DBAs can reduce the likelihood of recurring ORA-04031 incidents and improve database stability and performance.

Final DBA Recommendation

Treat ORA-04031 as a diagnostic warning that requires investigation—not simply as proof that the database needs more memory. Identify the affected SGA memory area, preserve the diagnostic evidence, investigate workload and SQL behavior, review memory configuration, and make controlled changes only when the evidence supports them.

Found this guide helpful? Explore our Oracle Error Codes Guide for more Oracle DBA troubleshooting guides, Oracle error solutions, and database administration resources.

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