Tables clustering is used on tables which are frequently joined using equi join.Indexes are used for faster data reterival and indexes are done based on the type of application used.If runing oltp use b-tree,if using dss use bitmap index.Indexes should be created on those colums which are frequently used in the where clause and should have higher cardinality.
I doubt that they realy improve the performanc, since there is no such type of index in Oracle. Clustered indexes exist in some other relational databases, but not in Oracle. The only "clustered" database object available in Oracle are clustered tables, as you were allready told.
Also, could you be a little more specific about your actual problems in the future? For such a broad questions probably the best answer you will get here will be links to Oracle documentation. But you can probably find and searc the documentation yourself, I guess.
Jurij Modic ASCII a stupid question, get a stupid ANSI
24 hours in a day .... 24 beer in a case .... coincidence?