Fields were added; update the DB table

What causes this issue?

The table structure was changed; fields were added to the end of the
table. If this termination occurred when you were activating a revised
version, select the function 'Append fields' and activate the table
online or enter the table for batch activation. If, on the other hand,
the termination occurred during reactivation of a table that was
already active, the table will have been activated in the ABAP/4
Dictionary, but the database table will not yet have been adapted.
Consequently, there is an inconsistency between the ABAP/4 Dictionary
table and the database table. The procedure described above can be
used here too.

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?

Error message extract from SAP system. Copyright SAP SE.