Error
Error Code: ORA-30009

Oracle ORA-30009: Insufficient Memory

📦 Oracle Database
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Description

The ORA-30009 error indicates that the Oracle database doesn't have enough memory to complete a string operation, typically within a hierarchical query. This often happens when processing many levels in a hierarchy or dealing with large string data.
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Error Message

ORA-30009: Not enough memory for string operation
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Known Causes

3 known causes
⚠️
Insufficient PGA Memory
The Process Global Area (PGA) allocated to the Oracle instance is too small to handle the memory demands of the query, particularly when `WORKAREA_SIZE_POLICY` is set to `AUTO`.
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Small Sort Area Size
When `WORKAREA_SIZE_POLICY` is set to `MANUAL`, the `SORT_AREA_SIZE` parameter might be insufficient for the sorting operations required by the query.
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Deep Hierarchy Levels
Queries involving deeply nested hierarchical data require significant memory to process all levels of the hierarchy, leading to memory exhaustion.
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Solutions

3 solutions available

1. Increase PGA_AGGREGATE_TARGET and PGA_AGGREGATE_LIMIT medium

Adjusting PGA memory parameters can resolve ORA-30009 by providing more memory for SQL operations.

1
Connect to your Oracle database as a user with SYSDBA privileges.
sqlplus / as sysdba
2
Check the current values of PGA_AGGREGATE_TARGET and PGA_AGGREGATE_LIMIT.
SHOW PARAMETER pga_aggregate_target;
SHOW PARAMETER pga_aggregate_limit;
3
Increase PGA_AGGREGATE_TARGET. A common starting point is to increase it by 20-30% or to a value that is roughly 40-60% of your total system RAM, ensuring you don't over-allocate.
ALTER SYSTEM SET pga_aggregate_target = <new_value_in_MB>M SCOPE=BOTH;
-- Example: ALTER SYSTEM SET pga_aggregate_target = 4096M SCOPE=BOTH;
4
Increase PGA_AGGREGATE_LIMIT to a value higher than PGA_AGGREGATE_TARGET. This acts as a safety net to prevent a single process from consuming excessive PGA.
ALTER SYSTEM SET pga_aggregate_limit = <new_value_in_MB>M SCOPE=BOTH;
-- Example: ALTER SYSTEM SET pga_aggregate_limit = 6144M SCOPE=BOTH; (ensure it's larger than pga_aggregate_target)
5
Restart the Oracle instance for the changes to take full effect if not using dynamic parameters or if you encounter issues. Note that `SCOPE=BOTH` typically makes changes effective immediately for new sessions.
SHUTDOWN IMMEDIATE;
STARTUP;

2. Tune SQL statements causing high PGA usage advanced

Identify and optimize specific SQL queries that are consuming excessive memory for string operations.

1
Identify sessions and SQL statements with high PGA usage. You can use V$PGASTAT and V$SESSION to monitor PGA consumption.
SELECT s.sid, s.serial#, s.username, s.program, p.pga_used_mem, p.pga_max_mem
FROM v$session s, v$process p
WHERE s.paddr = p.addr
ORDER BY p.pga_used_mem DESC;

-- To see PGA usage per SQL statement (may require tuning advisor or AWR reports for historical data)
SELECT sql_text, pga_allocated, rows_processed
FROM v$sqlarea
ORDER BY pga_allocated DESC;
2
Analyze the execution plan of the identified SQL statements. Look for operations that might involve large string manipulations, such as concatenations, conversions, or functions applied to large character data.
EXPLAIN PLAN FOR <your_problematic_sql_statement>;
SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY);
-- Analyze the output for cost and operations.
3
Optimize the SQL statement. This could involve:
1. Avoiding unnecessary string concatenations or conversions.
2. Using appropriate data types (e.g., VARCHAR2 with sufficient size, CLOB for very large strings).
3. Rewriting queries to reduce the amount of data processed or to use more efficient functions.
4. Ensuring proper indexing to reduce table scans and the need for extensive data manipulation.
5. If using PL/SQL, check for inefficient string handling within loops or procedures.
4
Test the optimized SQL statement to confirm that PGA usage has decreased and the ORA-30009 error is resolved.
Execute the optimized SQL statement and monitor PGA usage.

3. Review and Adjust SORT_AREA_SIZE and HASH_AREA_SIZE medium

While PGA_AGGREGATE_TARGET is the primary mechanism for PGA management, these older parameters can still influence memory allocation for specific operations.

1
Connect to your Oracle database as a user with SYSDBA privileges.
sqlplus / as sysdba
2
Check the current values of SORT_AREA_SIZE and HASH_AREA_SIZE.
SHOW PARAMETER sort_area_size;
SHOW PARAMETER hash_area_size;
3
If PGA_AGGREGATE_TARGET is not set or set to 0, increasing these parameters might be necessary for specific sort or hash join operations. However, if PGA_AGGREGATE_TARGET is set, Oracle generally manages these internally. Increasing them manually without a clear understanding can lead to over-allocation.
ALTER SYSTEM SET sort_area_size = <new_value_in_bytes> SCOPE=BOTH;
ALTER SYSTEM SET hash_area_size = <new_value_in_bytes> SCOPE=BOTH;
-- Example: ALTER SYSTEM SET sort_area_size = 10485760 SCOPE=BOTH; (10MB)
4
Monitor the database performance and PGA usage after making changes. It's generally recommended to rely on PGA_AGGREGATE_TARGET for automated memory management.
Use V$PGASTAT and V$SESSION to monitor memory usage.