Node component &1 used for Alternative key &2 (&3) has data type SSTRING

What causes this issue?

You use Node components with data type SSTRING (Character string) for an
Alternative Key definition. Either as part of a structured Alternative
Key or as line type.

System Response

The BOPF runtime shows "unexpected behavior" in key conversion (and
other functions) in case SSTRING-based data is handed over with trailing
spaces.
Root cause is, that a SSTRING-based value is "right trimmed" once it
gets stored in the database, so that subsequent comparisons in ABAP will
fail. In detail the comparisons fail in the BOPF data access layer (DAC)
and in the BOPF buffer.

How to fix this error?

Do not use Node components with data type SSTRING for an Alternative Key
definition. Neither as part of a structured Alternative Key nor as line
type.
If you require a SSTRING-based Node component for an Alternative Key
definition, you must change the data type from SSTRING to CHAR.
If the change from SSTRING to CHAR is not possible, make sure, that your
application hands over the SSTRING-based data to BOPF without trailing
spaces! In detail make sure, that all calls to the BOPF services
CONVERT_ALTERN_KEY, MODIFY, ... provide no trailing spaces in the
SSTRING-based components of the importing parameters IT_KEY,
IT_MODIFICATION-DATA, ...!

Procedure for System Administrators

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

Error message extract from SAP system. Copyright SAP SE.