John Mitchell-245523 (8/27/2014)
Some vendors are happy for you to do this; some aren't. At the very least, you should monitor performance and, where necessary, tweak the indexing or suggest changes to the vendor.John
We have quite of few vendor apps. Almost all of them specifically say do NOT change anything about the data structure or add additional indexes or you will no longer be supported.
Side note. If you have a vendors database and you do add indexes make sure you keep the scripts for these indexes. Reason I say that is when it comes time to do an application upgrade and that involves scripts they run against the db and do table alters those indexes may no longer exist afterwards.
Some small dbs we have had over the years have had very little indexes and some with no clustered indexes. Very poor designs. Some over index.... AND some are very good about indexing. It just depends.