Disadvantages of Indexes
This is only a consideration for secondary, join, and hash indexes in the Teradata Database environment. The more secondary, join, and hash indexes you have defined for a table, the larger the potential update maintenance downside becomes.
Because of this, secondary, join, and hash indexes are generally inappropriate for OLTP situations, though some limited use of secondary and sparse join indexes (when the sparse index is defined on columns that are rarely updated) might be appropriate.
You can optionally specify fallback on join and hash indexes as well. Join and hash indexes do not default to fallback if their underlying base tables are defined with fallback.
For these reasons, it is extremely important to use EXPLAIN request modifiers to determine optimum data manipulation statement syntax and index usage before putting those statements (and indexes) to work in a production environment.