Table "alias" has one or more non-structural indexes open. Please close them and retry the Begin Transaction (Error 1548)

Close all non-structural (non-.CDX) indexes and try the operation again.

If other indexes are open on the file, their writes will go directly to disk and will not be reflected in the table changes until you issue END TRANSACTION. Consequently, if a ROLLBACK is issued, the non-structural indexes will be incorrect.