Datatypes (1) : ROWID and UROWID

Oracle uses a ROWID datatype to store the address (rowid) of every row in the database.

Physical rowids store the addresses of rows in ordinary tables (excluding index-organized tables),
clustered tables, table partitions and subpartitions, indexes, and index partitions and
subpartitions.
Logical rowids store the addresses of rows in index-organized tables.
A single datatype called the universal rowid, or UROWID, supports both logical and physical rowids,
as well as rowids of foreign tables such as non-Oracle tables accessed through a gateway.

A column of the UROWID datatype can store all kinds of rowids. The value of the COMPATIBLE
initialization parameter must be set to 8.1 or higher to use UROWID columns.

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