How To Fix DB02126 - Snapshot too old. ORA-1555.

SAP Error Message - Details

• Message type: E = Error

• Message class: DB02 - For Oracle Component of the Database Monitor

• Message number: 126

• Message text: Snapshot too old. ORA-1555.

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• What is the cause and solution for SAP error message DB02126 - Snapshot too old. ORA-1555. ?

  The error message "DB02126 Snapshot too old. ORA-1555" is an Oracle database error that indicates a problem with the undo data required to construct a consistent read view of the data. This typically occurs in environments with high transaction rates where the undo data is overwritten before it can be used to satisfy a query.
  Cause:
  The ORA-1555 error occurs when:
  
  Long-Running Queries: A query is running for a long time and tries to access data that has been modified and the corresponding undo data has already been overwritten.
  Insufficient Undo Tablespace: The undo tablespace is too small to hold all the undo data needed for concurrent transactions and long-running queries.
  High Transaction Volume: A high volume of DML (Data Manipulation Language) operations can lead to rapid consumption of undo space.
  Improper Undo Retention Settings: The undo retention period is set too low, causing the database to overwrite undo data before it is needed.
  
  Solution:
  To resolve the ORA-1555 error, consider the following solutions:
  
  
  Increase Undo Tablespace:
  
  Increase the size of the undo tablespace to accommodate more undo data. This can be done by adding data files or resizing existing files.
  
  ALTER DATABASE DATAFILE 'path_to_undo_tablespace_file' RESIZE new_size;
  
  
  Adjust Undo Retention:
  
  Increase the UNDO_RETENTION parameter to ensure that undo data is retained for a longer period. This can help long-running queries to access the required undo data.
  
  ALTER SYSTEM SET UNDO_RETENTION = desired_value;
  
  
  Optimize Long-Running Queries:
  
  Review and optimize long-running queries to reduce their execution time. This can involve indexing, rewriting queries, or breaking them into smaller parts.
  
  
  
  Use Flashback Technology:
  
  If applicable, consider using Oracle's Flashback technology to retrieve data without relying on undo data.
  
  
  
  Monitor and Tune Transactions:
  
  Monitor the transaction volume and adjust application logic to minimize the number of concurrent DML operations that could lead to undo contention.
  
  
  
  Review Application Logic:
  
  Ensure that the application logic is not holding transactions open longer than necessary, which can exacerbate the issue.
  
  
  
  Related Information:
  
  Undo Tablespace: This is a special tablespace in Oracle that stores undo data. It is crucial for maintaining data consistency and supporting features like rollback and read consistency.
  Read Consistency: Oracle uses undo data to provide a consistent view of the data at the time a query started, which is essential for multi-user environments.
  Monitoring Tools: Use Oracle's monitoring tools (like AWR reports) to analyze undo usage and identify potential bottlenecks.
  
  By addressing the underlying causes and implementing the suggested solutions, you can mitigate the occurrence of the ORA-1555 error in your Oracle database environment.