How To Fix 00646 - No free block found, session terminated

SAP Error Message - Details

• Message type: E = Error

• Message class: 00 -

• Message number: 646

• Message text: No free block found, session terminated

Self-Explanatory Message

Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of messages in the SAP system have a message text, however this is frequently insufficient to comprehend or resolve the problem.

To make things easier, more detailed information is frequently added to describe the issue, how to fix it, and the necessary steps or configuration modifications.

Unfortunately, there isn't any extra information in this error notice.

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Smart SAP Assistant

• What is the cause and solution for SAP error message 00646 - No free block found, session terminated ?

  The SAP error message "00646 No free block found, session terminated" typically indicates that the SAP system has run out of memory or resources to allocate for a new session or process. This can occur in various scenarios, such as when the system is under heavy load, when there are memory leaks, or when the configuration settings for memory allocation are not optimized.
  Causes:
  
  Memory Exhaustion: The most common cause is that the SAP instance has exhausted its available memory resources.
  High Load: A sudden spike in user activity or background jobs can lead to resource exhaustion.
  Configuration Issues: Incorrect settings in the SAP profile parameters related to memory allocation (e.g., abap/heap_area_total, abap/heap_area_dia, etc.) can lead to insufficient memory.
  Memory Leaks: Poorly written custom code or third-party add-ons can lead to memory leaks, consuming resources over time.
  Database Issues: Problems with the underlying database can also contribute to resource issues.
  
  Solutions:
  
  Check System Load: Monitor the system load and user sessions. Use transaction codes like SM50 (Process Overview) and SM66 (Global Process Overview) to identify any long-running processes or bottlenecks.
  Increase Memory Allocation: Review and adjust the SAP profile parameters related to memory. You may need to increase the values for parameters like:
  
  abap/heap_area_total
  abap/heap_area_dia
  abap/heap_area_nondia
  
  
  Restart the Instance: If the system is under heavy load, a restart of the SAP instance may temporarily alleviate the issue.
  Analyze Custom Code: Review any custom ABAP code or third-party add-ons for potential memory leaks or inefficiencies.
  Database Optimization: Ensure that the database is properly tuned and that there are no issues affecting performance.
  System Monitoring: Implement monitoring tools to keep track of memory usage and system performance over time.
  
  Related Information:
  
  SAP Notes: Check SAP Notes for any known issues or patches related to this error. You can search for relevant notes in the SAP Support Portal.
  Transaction Codes: Familiarize yourself with transaction codes that can help diagnose memory issues, such as:
  
  ST02 (Tune Summary)
  ST04 (Database Performance)
  SM21 (System Log)
  
  
  SAP Community: Engage with the SAP Community for insights and shared experiences from other users who may have encountered similar issues.
  
  If the problem persists after trying the above solutions, it may be necessary to engage SAP support for further assistance.