Oracle Checkpoint: Can We Gather Dictionary Statistics in Oracle Autonomous Database?

One of the most common Oracle DBA maintenance tasks in traditional databases is gathering optimizer statistics.

DBAs often run:

DBMS_STATS.GATHER_DICTIONARY_STATS

to collect statistics for Oracle data dictionary objects.

But what happens if we try the same operation inside Oracle Autonomous Database?

In this blog, we will explore:

What dictionary statistics are
Why they are important
What happens in Autonomous Database
Why ORA-20000 occurs
Understanding ORA-06512 stack traces
How Autonomous Database handles statistics internally
Important architectural differences from traditional Oracle databases

Attempting to Gather Dictionary Statistics

Let us execute the following PL/SQL block:

SQL> begin
  2      dbms_stats.gather_dictionary_stats;
  3  end;
  4  /

The Error Output

begin
*
ERROR at line 1:

ORA-20000: Insufficient privileges to analyze
"AUDSYS"."AUD$UNIFIED"."SYS_P16148"(TABLE) in Dictionary Schema

ORA-06512: at "SYS.DBMS_STATS", line 51408
ORA-06512: at "SYS.DBMS_STATS", line 51363
ORA-06512: at "SYS.DBMS_STATS", line 46595
ORA-06512: at "SYS.DBMS_STATS", line 45745
ORA-06512: at "SYS.DBMS_STATS", line 46470
ORA-06512: at "SYS.DBMS_STATS", line 51295
ORA-06512: at "SYS.DBMS_STATS", line 51398
ORA-06512: at line 2

Understanding ORA-20000

According to Oracle documentation, ORA-20000 is a generic user-defined error raised by PL/SQL packages when an operation cannot proceed successfully.

Official Oracle documentation:

https://docs.oracle.com/error-help/db/ora-20000/

In this specific case, the message clearly states:

Insufficient privileges to analyze
"AUDSYS"."AUD$UNIFIED"

This means the current user does not have sufficient permissions to gather statistics on Oracle internal dictionary objects.

Understanding ORA-06512

The ORA-06512 messages are PL/SQL stack trace entries.

Official Oracle documentation:

https://docs.oracle.com/error-help/db/ora-06512/

ORA-06512 itself is not the root error.

Instead, it shows:

Which PL/SQL package failed
The internal line number
The execution path of the error

Example:

ORA-06512: at "SYS.DBMS_STATS", line 51408

This tells us the failure happened internally inside the:

SYS.DBMS_STATS

package implementation.

What is GATHER_DICTIONARY_STATS?

The procedure:

DBMS_STATS.GATHER_DICTIONARY_STATS

collects optimizer statistics for:

SYS objects
Data dictionary tables
Internal Oracle metadata
System schemas

These statistics help the Oracle optimizer generate efficient execution plans for internal SQL operations.

Why DBAs Use Dictionary Statistics

In traditional Oracle databases, DBAs may gather dictionary stats:

After upgrades
After patching
After catalog changes
During performance tuning
After large metadata changes

Example in traditional databases:

EXEC DBMS_STATS.GATHER_DICTIONARY_STATS;

This operation is usually performed by:

SYS
SYSDBA

Why Does It Fail in Autonomous Database?

Oracle Autonomous Database is a fully managed platform.

Oracle intentionally restricts access to:

Internal dictionary schemas
Oracle-managed objects
System statistics maintenance
Low-level database administration

Even users with:

DBA role

do not receive complete SYSDBA-level privileges.

The AUDSYS Schema Explained

The error references:

AUDSYS.AUD$UNIFIED

This belongs to Oracle Unified Auditing infrastructure.

Oracle protects these internal audit tables because they are critical for:

Security auditing
Compliance
Internal monitoring
Cloud governance

Allowing unrestricted analysis or modification could impact:

Performance
Security
Cloud automation
Audit integrity

Important Autonomous Database Concept

In Autonomous Database:

Oracle itself manages optimizer statistics automatically.

This includes:

Dictionary statistics
System statistics
Fixed object statistics
Optimizer maintenance
Automatic statistics gathering jobs

Customers are intentionally prevented from modifying many internal optimizer components.

Traditional Oracle vs Autonomous Database

Feature	Traditional Oracle DB	Autonomous Database
SYSDBA Access	Available	Restricted
Gather Dictionary Stats	Allowed	Restricted
Analyze SYS Objects	Possible	Blocked
Optimizer Maintenance	DBA Managed	Oracle Managed
Internal Audit Tables Access	SYS Only	Protected by Oracle

Can We Gather User Schema Statistics?

Yes.

Autonomous Database allows gathering statistics for user-owned schemas and tables.

Example:

BEGIN
    DBMS_STATS.GATHER_SCHEMA_STATS('TEST_USER');
END;
/

or:

EXEC DBMS_STATS.GATHER_TABLE_STATS('TEST_USER','EMP');

These operations are fully supported for customer schemas.

What Statistics Does Autonomous Database Manage Automatically?

Oracle Autonomous Database automatically handles:

Optimizer statistics collection
Statistics refresh
Histogram management
SQL plan optimization
Adaptive optimizer tuning
Automatic indexing
Dictionary statistics

This is one of the major benefits of Autonomous Database.

Why Oracle Restricts Internal Statistics Operations

Oracle Autonomous Database is built around:

Automation
Self-healing infrastructure
Managed operations
Security isolation
Cloud-scale consistency

Allowing customers to directly manipulate internal dictionary statistics could:

Destabilize optimizer behavior
Break cloud automation
Impact multi-tenant infrastructure
Create unpredictable execution plans

Understanding the Full Error Stack

The sequence:

ORA-20000
ORA-06512
ORA-06512
ORA-06512

should be interpreted as:

ORA-20000 = Root failure reason
ORA-06512 = PL/SQL execution trace information

This is extremely common in Oracle PL/SQL package errors.

Best Practices in Autonomous Database

Allow Oracle to manage dictionary statistics automatically
Avoid attempting SYS-level maintenance operations
Gather statistics only for user schemas when needed
Use automatic optimizer management whenever possible
Focus on application-level tuning instead of internal database maintenance

What Makes Autonomous Database Different?

Traditional DBAs are used to:

Managing optimizer statistics manually
Running maintenance scripts
Gathering fixed object stats
Controlling optimizer behavior

Autonomous Database changes this model completely.

Oracle now automates:

Statistics gathering
Performance tuning
Index optimization
Storage management
Patch management
Security operations

Key Takeaways

DBMS_STATS.GATHER_DICTIONARY_STATS fails in Autonomous Database
ORA-20000 indicates insufficient privileges on internal dictionary objects
ORA-06512 provides PL/SQL stack trace information
AUDSYS objects are protected by Oracle
Oracle automatically manages dictionary statistics internally
User schema statistics gathering is still supported
Autonomous Database restricts many SYS-level DBA operations

Conclusion

Oracle Autonomous Database fundamentally changes the DBA operating model.

Operations that were traditionally performed manually — such as gathering dictionary statistics — are now handled automatically by Oracle Cloud infrastructure.

The ORA-20000 error shown while executing:

DBMS_STATS.GATHER_DICTIONARY_STATS

is expected behavior in Autonomous Database and demonstrates Oracle’s managed-cloud architecture.

Instead of manually maintaining internal optimizer statistics, DBAs can now focus more on:

Application design
SQL tuning
Data modeling
Analytics
Business workloads

while Oracle handles the complex internal database maintenance automatically behind the scenes.

Oracle Checkpoint

Sunday, 24 May 2026

Can We Gather Dictionary Statistics in Oracle Autonomous Database?