EBS ORA-01555: snapshot too old

What is EBS ORA-01555: snapshot too old

Understanding Oracle E-Business Suite (EBS)

Oracle E-Business Suite (EBS) is a comprehensive suite of integrated business applications designed to automate and streamline business processes. It includes modules for financials, supply chain management, human resources, and more, providing a unified platform for enterprise resource planning (ERP).

Identifying the ORA-01555 Error

The ORA-01555 error, commonly known as the 'snapshot too old' error, is a frequent issue encountered in Oracle databases. This error typically arises during long-running queries when the required undo data is no longer available, leading to query failure.

Symptoms of ORA-01555

When this error occurs, users may observe the following symptoms:

Queries fail with the error message: ORA-01555: snapshot too old. Performance degradation in database operations. Inconsistent query results.

Explaining the ORA-01555 Error

The ORA-01555 error is caused by insufficient undo data retention. When a query requires a consistent snapshot of the data, it relies on undo records to reconstruct the data as it existed at the start of the query. If these undo records are overwritten due to space constraints, the query cannot complete successfully.

Root Causes

The primary reasons for this error include:

Insufficient undo tablespace size. Long-running queries that exceed the undo retention period. High transaction rates leading to rapid undo data turnover.

Steps to Resolve ORA-01555

To resolve the ORA-01555 error, consider the following steps:

1. Increase Undo Tablespace Size

Increasing the size of the undo tablespace can help retain undo data longer. Use the following SQL command to resize the undo tablespace:

ALTER DATABASE DATAFILE '/path/to/undo01.dbf' RESIZE 2G;

Ensure that the path and size are adjusted according to your database configuration.

2. Optimize Long-Running Queries

Review and optimize queries to reduce their execution time. Consider breaking down complex queries or using indexes to improve performance.

3. Adjust Undo Retention

Modify the undo retention period to ensure that undo data is retained long enough for queries to complete:

ALTER SYSTEM SET UNDO_RETENTION = 3600;

This command sets the undo retention period to 3600 seconds (1 hour).

Additional Resources

For further reading and detailed guidance, refer to the following resources:

Oracle Documentation on Managing Undo Tablespace Oracle Community Discussion on ORA-01555