Technical data

17 Managing JMS

17-20 Administration Guide

JMS message paging saves memory for both persistent and non-persistent messages,

as even persistent messages cache their data in memory. Paged persistent messages

continue to be written to the regular backing store (file or database); and paged

non-persistent messages are written to the JMS server’s messsage paging store, which

is configured separately.

A paged-out message does not free all of the memory that it consumes. The message

header and message properties remain in memory for use with searching, sorting, and

filtering.

IConfiguring Paging

Unless paging is configured and enabled, all messages (even persistent ones) are held

in memory. You can configure paging for a new or existing JMS server and/or its

destinations through the Administration Console. Using the attributes on the JMS

Server node you can specify a paging store for a JMS server, enable bytes and/or

messages paging, and configure bytes/messages high and low thresholds to start and

stop paging.

Similarly, using the attributes on the Destinations node, you can configure

bytes/messages paging for all topics and queues configured on a JMS server. The

destinations use the paging store that is configured for the JMS server.

Also, if you use JMS templates to configure multiple destinations, you can use the

attributes on the Templates node to configure paging quickly on all your destinations.

To override a template’s paging configuration for specific destinations, you can enable

or disable paging on any destination.

For instructions on configuring a new JMS server, templates, and destinations (Topics

or Queues), see “JMS Servers,” “JMS Destinations,” and “JMS Templates” in the

Administration Console Online Help.

Note: For performance tuning purposes, you can modify the paging thresholds to any

legal value at any time. Once paging is enabled, however, you cannot

dynamically disable it by resetting a byte or message threshold back to -1. To

prevent paging from occurring, set the byte/message high threshold to a very

large number (maximum is 2

-1), so that paging is not triggered.