How To Fix WPS01121 - Parent task list key &1 / ext. ID &2: Enqueue error

SAP Error Message - Details

• Message type: E = Error

• Message class: WPS01 - Revision Planning - Task List Hierarchy

• Message number: 121

• Message text: Parent task list key &1 / ext. ID &2: Enqueue error

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.

What else can you do?

First, use our AnswerBot below to get a possible cause and solution (requires a premium subscription).

Also, review the in-depth Common Questions & Answers listed below; you could discover a solution there or be able to connect with others who have faced similar challenges.

You can also try searching the SAP support portal (support.sap.com) but you need a special user ID to access it. It is possible that an SAP support note exists that provides additional details about the mistake or even steps for fixing it.

Smart SAP Assistant

• What is the cause and solution for SAP error message WPS01121 - Parent task list key &1 / ext. ID &2: Enqueue error ?

  Certainly! Here's a detailed explanation for the SAP error message:
  
  SAP Error Message:
  WPS01121 Parent task list key &1 / ext. ID &2: Enqueue error
  
  Meaning / Cause:
  
  This error occurs when the system tries to lock (enqueue) a parent task list but fails.
  The enqueue error indicates that the lock on the parent task list key (with the given external ID) could not be obtained because it is already locked by another user or process.
  This situation typically arises in maintenance task list processing or work scheduling scenarios where multiple users or background jobs attempt to access or modify the same task list simultaneously.
  The enqueue mechanism in SAP is designed to prevent data inconsistencies by serializing access to certain objects. If the lock is held by another session, the enqueue request will fail, resulting in this error.
  
  
  Common Causes:
  
  Another user or process currently holds the lock on the parent task list.
  Long-running transaction or job that locked the task list and did not release it yet.
  Deadlock or system performance issues causing locks to be held longer than usual.
  Improper termination of a session that left locks hanging.
  Custom code or enhancements that do not properly handle enqueue/dequeue operations.
  
  
  Solution / How to Resolve:
  
  
  Check who holds the lock:
  
  Use transaction SM12 (Lock Entries) to find the lock entries related to the parent task list key.
  Search by the object name related to task lists (e.g., PLKO or specific enqueue objects like ENQUEUE_EPLKO).
  Identify the user/session holding the lock.
  
  
  
  Release the lock if appropriate:
  
  If the lock is held by a user who is no longer working on it or by a stuck session, you can delete the lock entry in SM12.
  Be cautious: deleting locks can cause data inconsistencies if the user is still working on the object.
  
  
  
  Coordinate with users:
  
  Inform users or administrators about the lock and ask them to finish or terminate their sessions properly.
  
  
  
  Check for long-running jobs or batch processes:
  
  Identify background jobs or batch processes that might be locking the task list.
  Reschedule or terminate if necessary.
  
  
  
  Review custom code:
  
  If custom developments are involved, ensure enqueue and dequeue calls are correctly implemented.
  
  
  
  System performance:
  
  If locks are held for too long due to system slowness, investigate and resolve performance bottlenecks.
  
  
  
  
  Additional Information:
  
  Enqueue mechanism: SAP uses enqueue objects to lock business objects during update or change operations to ensure data consistency.
  Task lists: In SAP PM (Plant Maintenance) or PP (Production Planning), task lists are used to define sequences of operations or maintenance steps.
  Related transactions:
  
  SM12: Display and delete lock entries.
  SM21: System log to check for system errors.
  SM13: Update errors.
  SM37: Background job monitoring.
  
  
  SAP Notes: Check SAP OSS notes for any known bugs or patches related to enqueue errors on task lists.
  
  
  Summary:
  
  
  
  Aspect
  Details
  
  
  
  
  Error
  WPS01121 Parent task list key &1 / ext. ID &2: Enqueue error
  
  
  Cause
  Lock on parent task list could not be obtained because it is already locked
  
  
  Solution
  Check and release locks in SM12; coordinate with users; check background jobs; review custom code
  
  
  Related Info
  Enqueue mechanism, task list processing, transactions SM12, SM37, SAP Notes
  
  
  
  
  If you need help with specific steps or further troubleshooting, feel free to ask!