Message type: E = Error
Message class:  RSODSO_GUI - UI related messages 
Message number: 016
Message text: Index ID &1 already exists. Choose another one.
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.
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.
The SAP error message RSODSO_GUI016 indicates that there is an attempt to create or modify an index in a DataStore Object (DSO) where the specified Index ID already exists. This typically occurs in the context of SAP BW (Business Warehouse) when working with DataStore Objects.
Cause: The error is caused by trying to create an index with an ID that is already in use within the same DSO. Each index in a DSO must have a unique identifier, and if you attempt to create a new index with an ID that is already assigned to another index, the system will throw this error.
Solution: To resolve this error, you can take the following steps: Check Existing Indexes: Go to the DataStore Object in question and check the existing indexes. You can do this by navigating to the DSO in the SAP BW modeling tools and reviewing the index definitions. Choose a Different Index ID: If you are
 Get instant SAP help. Sign up for our Free Essentials Plan.
Get instant SAP help. Sign up for our Free Essentials Plan. 
RSODSO_GUI015 Field name already exists at position &1. Choose a different name.
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
RSODSO_GUI014 Index &1 deleted
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
RSODSO_GUI017 No fields maintained. Enter a valid field name before saving the object.
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
RSODSO_GUI018 No semantical key field selected. Choose at least one field.
Self-Explanatory Message Since SAP believes that this specific error message is 'self-explanatory,' no more information has been given.The majority of...
Click on this link to search all SAP messages.