U

UGA

See User Global Area (UGA).

Undo Advisor

A tool within the Oracle advisory framework that uses past undo usage to recommend settings for the UNDO_RETENTION parameter as well as an optimal size for the undo tablespace.

undo data

The data blocks changed or updated, along with pointers to rows inserted that are stored in an undo tablespace to support read consistency, rolling back, and recovery from failed transactions or an instance crash. Also referred to as rollback information.

undo segment

The segment that stores the before image of modified data; used for rollback or transaction recovery purposes.

undo tablespace

A special type of tablespace that holds undo data. Only one undo tablespace can be active in the database at any given time.

user error

A user operation that does not generate an error message, but whose result was unintended, such as accidentally dropping a table.

User Global Area (UGA)

An area in either the SGA (System Global Area) or PGA (Program Global Area) used to keep track of session-specific information. See also Program Global Area (PGA); System Global Area (SGA).

User Process

The process that runs on the client computer or application server and connects to the instance using a Server Process.

user process failure

The failure of a single connection to the database.