N

nested savepoint

A savepoint that is included or positioned within another savepoint. Nested savepoints allow an application to have multiple levels of savepoints active at a time and allow the application to roll back to any active savepoint as desired.

nested table expression

A fullselect in a FROM clause (surrounded by parentheses).

network address

An identifier for a node in a network.

network addressable unit (NAU)

The origin or the destination of information transmitted by the path control network. An NAU can be a logical unit (LU), physical unit (PU), control point (CP), or system services control point (SSCP).

Network File System (NFS)

A client/server application that lets all network users access shared files stored on computers of different types. Users can manipulate shared files as if they were stored locally on the user's own hard disk.

Network Identifier

In a z/OS or OS/390 environment, the network identifier that is assigned by IMS or CICS, or if the connection type is RRSAF, the z/OS and OS/390 RRS unit of recovery identifier (URID).

Network Information Service (NIS/NIS+)

On AIX, a central record of passwords, nodes, and related data that can be used with the DB2 Administration Server to administer user and group names.

network name

In SNA, a symbolic name by which users refer to a network addressable unit (NAU), a link station, or a link.

network node (NN)

In APPN, a node on the network that provides distributed directory services, topology database exchanges with other APPN network nodes, and session and routing services.

Network Node Server

An APPN network node that provides network services for its local logical units and adjacent end nodes.

network-qualified name

The name by which an LU is known throughout an interconnected SNA network. A network-qualified name consists of a network name identifying the individual subnetwork and a network LU name. Network-qualified names are unique throughout an interconnected network. Also known as the network-qualified LU name or fully qualified LU name.

network services

The services within network addressable units that control network operation through SSCP-to-SSCP, SSCP-to-PU, SSCP-to-LU, and CP-to-CP sessions.

New Technology File System (NTFS)

One of the native file systems in Windows NT and later operating environments such as Windows 2000.

NFS

See [Network File System]

nickname

(1) In a federated system, an identifier in a query that refers to an object at a data source. The objects that nicknames identify are referred to as data source objects. Examples of data source objects include tables, views, synonyms, table-structured files, and search algorithms.

(2) A name defined in the DB2 Information Integrator that represents a physical database object (such as a table or stored procedure) in a non-DB2 relational database.

NID

See [network identifier]

NIS/NIS+

See [Network Information Service]

NN

See [network node]

node

(1) In communications, an end point of a communications link, or a junction common to two or more links in a network. Nodes can be processors, communication controllers, cluster controllers, terminals, or workstations. Nodes can vary in routing and other functional capabilities.

(2) In hardware, a uniprocessor or symmetric multiprocessor (SMP) computer that is part of a clustered system or a massively parallel processing (MPP) system. For example, RS/6000 SP is a MPP system that consists of nodes connected by a high-speed network.

(3) An obsolete term for database partition.

node directory

A directory that contains information that is necessary to establish communications from a client workstation to all applicable database servers.

nodegroup

An obsolete term for database partition group.

noncumulative backup image

See [delta backup]

non-DB2 relational database server

An Informix database server or a relational database server from a vendor other than IBM.

non-delimited ASCII (ASC)

ASC file format is also known as fixed-length ASCII file format because each column length in the file has the same length as defined for the corresponding column definition in the table.

nonleaf page

A page that contains keys and page numbers of other pages in the index (either leaf or nonleaf pages). Nonleaf pages never point to actual data.

normalization

The process of restructuring a data model by reducing its relations to their simplest forms. It is a key step in the task of building a logical relational database design. Normalization helps avoid redundancies and inconsistencies in your data. An entity is normalized if it meets a set of constraints for a particular normal form (first normal form, second normal form, and so on).

See also [denormalization]

notification log

See [administration notification log]

NTFS

See [New Technology File System]

null

A value that indicates the absence of information.

nullable

The condition in which a value for a column, function parameter, or result can have an absence of a value.