Message type: E = Error
Message class:  EHSBM_TX - Messages on ActiveX Tree Control 
Message number: 021
Message text: Select only one node or entry
You attempted to apply an activity to several selected entries of the
tree.
The activity is permitted for single nodes or entries in the tree only.
Select only individual nodes or tree entries with the mouse.
Error message extract from SAP system. Copyright SAP SE.
The SAP error message EHSBM_TX021 ("Select only one node or entry") typically occurs in the context of the SAP Environment, Health, and Safety (EHS) module, particularly when working with the EHS Management or EHS Product Safety functionalities. This error indicates that the system expects the user to select only one node or entry from a list or hierarchy, but multiple selections have been made.
Cause:
Multiple Selections: The most common cause of this error is that the user has selected more than one item or node in a tree structure or list where only a single selection is allowed.
User Interface Restrictions: Certain screens or transactions in SAP EHS are designed to allow only single selections for specific operations, and attempting to select multiple entries triggers this error.
Configuration Issues: In some cases, the configuration of the EHS module may not be set up correctly, leading to unexpected behavior.
Solution:
Single Selection: Review your selections and Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
EHSBM_TX020 Cannot find node
What causes this issue?  You attempted to execute an activity on a node of the tree that was not found.How to fix this error?  Check whether you selec...
EHSBM_TX001 are stored in this message class.
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
EHSB_RC000 Internal error; notify your system administrator
What causes this issue?  More system information: &V1&; &V2&; &V3&; &V4&System Response  The system issues an error me...
EHSB_RC001 Spec.search using constr.-val. params for class &1 not possible (exc. &3)
What causes this issue?  The search for substances with constraints using constraint-validity parameters for class &v1& , class type &v2&a...
Click on this link to search all SAP messages.