What data access methods Informix have ?

Hi, there, In Ingres, for each table, it may be exist in four types of data orgnisations, their heap, hash, isam, btree. In addition, indexes can be created for other attributes as one of these four types. I am reading an Informix book now. it does not address this issue very clearly. can any one tell me : what type data orgnisations Informix can have ? what indexing methods could be build for each table ? Thanks. Jiang