The Data View object allows defining all the information related to an external table in order to access it as any other table created by GeneXus.
As we all know, upon defining transactions, tables are created in the database that is associated with an Environment. In some cases we may need to work with existing tables that are not included in our data model, and which are called "external tables." They may belong to another model or version, or they may not be created by GeneXus.
Even though GeneXus cannot reorganize these tables, it can query them and make additions, deletions and changes.
There are two ways to work with an external table: with an associated Transaction to make additions, deletions and changes to this table, or without an associated Transaction. In this case, these operations can only be made through procedures, and not with the usual commands but with others. The most common reasons for which Data Views are defined without an associated transaction are when it's necessary to access an external table that has no indexes, or when it's necessary to access external tables, only once, just to define load processes (that is, batch processes that run through external tables and load tables of the Environment). Clearly, in these cases it's not necessary to have interactive access to the external tables, but only through batch load processes; and lastly, another reason to do so is when we don't need this file to participate in the data model normalization.
Data Views do not necessarily handle a table that belongs to a database; even though it happens most of the time, it can also be a text file or another type of file.