Error in index '2' of table &

What causes this issue?

You must create an index for table &V1&. This index is named '2'. The
index must contain the following fields:
Index 2:
DOCNR
RYEAR
DOCCT
RBUKRS/RCOMP for local/global tables
RLDNR
ROBUKRS only for global tables
RCLNT
DOCLN
RPMAX (only for plan line item tables)

System Response

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

How to fix this error?

Note the above requirements.

Error message extract from SAP system. Copyright SAP SE.