in startsap/stopsap command line executable , the ... - BeKnowledge
in startsap/stopsap command line executable , the ... - BeKnowledge
in startsap/stopsap command line executable , the ... - BeKnowledge
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Central Services<br />
• The Central Services run on one host and form a separate Java <strong>in</strong>stance. They<br />
consist of <strong>the</strong> message service and <strong>the</strong> enqueue service.<br />
• The Central Services provide <strong>the</strong> basis for communication and synchronization<br />
for <strong>the</strong> Java cluster:<br />
– The message service adm<strong>in</strong>isters a list of <strong>the</strong> dispatchers and <strong>the</strong> server<br />
processes of <strong>the</strong> Java cluster. It represents <strong>the</strong> <strong>in</strong>frastructure of data<br />
exchange (for small quantities of data) between <strong>the</strong> nodes <strong>in</strong>volved. In <strong>the</strong><br />
case of load balanc<strong>in</strong>g between a large number of Java <strong>in</strong>stances, it also<br />
provides <strong>the</strong> load balanc<strong>in</strong>g <strong>in</strong>formation for <strong>the</strong> SAP Web Dispatcher.<br />
– The enqueue service adm<strong>in</strong>isters logical locks that are set <strong>in</strong> a server<br />
process by <strong>the</strong> executed application program. It is also used for cluster-wide<br />
synchronization.<br />
• The Central Services are essentially required when a Java cluster is <strong>in</strong>stalled.<br />
They are started on a host with a separate system number and <strong>the</strong> system ID<br />
(SID) of <strong>the</strong> entire system. If <strong>the</strong> Central Services are runn<strong>in</strong>g, o<strong>the</strong>r Java<br />
<strong>in</strong>stances are started with <strong>the</strong> program JControl (see <strong>the</strong> unit Start<strong>in</strong>g and<br />
Stopp<strong>in</strong>g a SAP NetWeaver AS Java).<br />
18 October 2010