RowSet methods throw SQLFeatureNotSupportedException which isn't specified.
This issue cause 21 conformance test failures for JCK8, the following APIs are affected:

(1) javax.sql.rowset.BaseRowSet
setNClob()
setNString()
setNCharacterStream()
setNCharacterStream()
setRowId()
setSQLXML()

(2) javax.sql.rowset.serial.SerialBlob
free()

(3) javax.sql.rowset.serial.SerialClob
free()

(4) javax.sql.rowset.serial.SQLInputImpl
readNString()
readNClob()
readRowId()
readSQLXML()
readURL()

(5) javax.sql.rowset.serial.SQLOutputImpl
writeNClob()
writeNString()
writeObject()
writeRowId()
writeSQLXML()

list of failed tests is in 'comments' section