Availability Guide for Application Design

Glossary
Availability Guide for Application Design—525637-004
Glossary-2
audit record
audit record. A before-image, an after-image, or control information for a transaction. Audit
records are stored in audit-trail files.
audit trail. A record of database changes that can be used by the TMF product to rebuild a
database in the event of a hardware or software failure.
audit-trail file. A disk file containing audit records for transactions that make changes to
audited disk files.
availability. The amount of time an application running on a HP system can be used
effectively by the user of that application.
babbling node. A network node that is transmitting random, meaningless packets onto the
network. Babbling nodes are often caused by a defective LAN card.
back-end process. A process that serves as the intermediary between an application
process and communication lines, providing connectivity to a message switching
system or some other back-end service. Contrast with front-end process.
backup process. The member of a process pair that takes over the application work when
the primary process fails. See also primary process and process pair.
batch window. A period of time for which the online part of an application is traditionally
brought down in order to run batch operations.
BB. See bulletin board (BB).
BBL. See bulletin board liaison (BBL).
before-image. A copy or copied portion of a database record that is made by the TMF
product before a transaction changes the record. See also after-image.
broadcast storm. The resulting traffic on the network when the technique of broadcasting
special messages to all hosts on a network has been overused. Such overuse has the
potential to disable the network. Broadcast storms are usually caused by software
errors.
B-tree. An associative file-access structure that provides keyed and key-sequenced
sequential access to data. B-trees cluster records with similar keys together. B-trees
balance the search depth so that all accesses take only a few page accesses to find a
record.
bulletin board (BB). A collection of shared data structures that maintain configuration and
status information about a running NonStop Tuxedo application. Information in the
bulletin board is updated as the dynamics of the application change. The bulletin board
is replicated on every processor that supports the application.
bulletin board liaison (BBL). The NonStop Tuxedo System /T administrative process
responsible for maintaining a copy of the bulletin board on a specific processor. The