How To Fix HH055 - Informix 'read ahead' feature seems to be switched off

SAP Error Message - Details

• Message type: E = Error

• Message class: HH - (Long) text for check tool 'infcfgcheck'

• Message number: 055

• Message text: Informix 'read ahead' feature seems to be switched off

What causes this issue?

This message is not an error!
The quality of the Informix feature 'Read ahead' could not be
determined since this feature seems to be switched off
on your system.

System Response

How to fix this error?

Error message extract from SAP system. Copyright SAP SE.

Smart SAP Assistant

• What is the cause and solution for SAP error message HH055 - Informix 'read ahead' feature seems to be switched off ?

  The SAP error message HH055 indicates that the 'read ahead' feature for Informix is turned off. This feature is important for optimizing database performance, as it allows the database to pre-fetch data pages into memory, reducing the number of disk I/O operations and improving response times for queries.
  Cause:
  The error can occur due to several reasons:
  
  Configuration Settings: The Informix database may not have the 'read ahead' feature enabled in its configuration settings.
  Database Version: Certain versions of Informix may have different default settings or may not support the 'read ahead' feature.
  Resource Limitations: If the system is under heavy load or if there are resource constraints, the database may disable certain features to maintain stability.
  
  Solution:
  To resolve the HH055 error, you can take the following steps:
  
  
  Check Configuration:
  
  Verify the Informix configuration settings. You can check the ONCONFIG file for the READAHEAD parameter. It should be set to a value greater than 0 to enable the feature.
  Example: 
  READAHEAD 1
  
  
  
  
  Modify Configuration:
  
  If the READAHEAD parameter is set to 0, change it to a positive value (e.g., 1 or higher) and restart the Informix database server for the changes to take effect.
  
  
  
  Database Version:
  
  Ensure that you are using a version of Informix that supports the 'read ahead' feature. If necessary, consider upgrading to a newer version.
  
  
  
  Monitor System Resources:
  
  Check the system's resource usage (CPU, memory, disk I/O) to ensure that the database has enough resources to operate efficiently. If the system is under heavy load, consider optimizing queries or increasing system resources.
  
  
  
  Consult Documentation:
  
  Refer to the official Informix documentation for detailed information on configuring the 'read ahead' feature and other performance tuning options.
  
  
  
  Related Information:
  
  Performance Tuning: Enabling 'read ahead' is just one aspect of performance tuning in Informix. Other parameters and settings may also need to be adjusted based on your specific workload and usage patterns.
  SAP Notes: Check SAP Notes for any specific recommendations or patches related to this error message.
  Database Monitoring Tools: Utilize database monitoring tools to analyze performance and identify bottlenecks that may be affecting the database's ability to utilize features like 'read ahead'.
  
  By following these steps, you should be able to resolve the HH055 error and improve the performance of your SAP system using Informix.