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EMS Manual

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EMS Manual—426909-005
5-1
5 Compiled Filters
This section describes compiled filters. For a detailed description of filter tables and
burst filters, see Section 6, Filter Tables and Burst Filters.
Writing and Compiling Filters
The filter language and compiler are used to construct compiled filters.
Filter Operation
This subsection describes the environment in which compiled filters run.
Event Message Filters
A compiled filter is a program that runs interpretively in a collector or distributor while
that collector or distributor reads event messages. Filters select or reject messages,
depending on criteria that you specify in a filter specification. When compiled filters are
used, the filter specification must be compiled by the filter compiler, and the filter object
(or filter) must be loaded into the collector or distributor before filter operation can
begin.
EMS filters, including filter tables and burst filters, reduce message traffic within a
system and over the network by placing part of the program logic as close to the
source of event messages (a collector or distributor) as possible. Rejected messages
are skipped, while selected messages proceed to their destinations. For collector
filters, the destination for selected events is the collector’s log file. The destination for
messages selected by distributor filters depends on the distributor type:
Consumer distributors return selected event messages in response to GETEVENT
command messages. Each response message contains at most one event
message.
Printing distributors send the selected event messages—in the form of display
text—to TEXTOUT destinations.
Forwarding distributors send the selected event messages to a primary collector
on another system (node) or to an alternate collector on the same node.
Topic Page
Writing and Compiling Filters
5-1
The Filter Language 5-7
The Filter Compiler 5-44
Note. Symbolic names in this section are in TACL form, using circumflex (^) symbols rather
than hyphens, because of the interface to TACL of the filter language.