# SAP Instance

An SAP Instance is an administrative unit that groups components of an SAP System that provide one or more services, as defined in the SAP Glossary:

> Administrative unit that groups components of an SAP system running on one physical host. Application server instances provide the actual computing capabilities of a system and offer corresponding services. Instances are started, stopped, and monitored as one unit. There can be multiple instances (belonging to the same or to different systems) on one host. An instance can be uniquely identified by the host name and a two-digit instance number.

— SAP Glossary

An SAP Instance can be one of the types listed below. An SAP Instance is hosted by exactly one Physical Server or Virtual Cluster Server, but multiple SAP Instances can be hosted on the same server.

If you want to manage or monitor an SAP Instance, you need to manage or monitor the Physical Server or the Virtual Cluster Server that the SAP Instance is hosted on.

Avantra supports the following SAP Instance Types:

Central | An SAP Web Application Server ABAP instance. The one marked as Central by Avantra is usually the primary Application Server as well. The term Central is still used by Avantra to indicate that this is the Application Server where the SAP System related checks are executed.
Central+Java | Same as the SAP Web Application Server ABAP CENTRAL instance above, but includes a Java stack as SAP NetWeaver Add-In installation. Central+Java instance types are deprecated by SAP. It is recommended to run separate ABAP or Java systems.
Dialog | An instance of an SAP Web Application Server ABAP that is not the central instance
Dialog+Java | An instance of an SAP NetWeaver Add-In installation with ABAP and Java stack that is not the central instance.
Java | An instance of an SAP Web Application Server Java.
Java_Scs | A (Java) SAP Central Services instance.
Abap_Scs | An ABAP SAP Central Services instance.
Trex | A TREX engine.
Web Dispatcher | An SAP Web Dispatcher instance.
Abap_Scs with Web Dispatcher | An ABAP SAP Central Services with integrated Web Dispatcher.
Enqueue Replication Server | An Enqueue Replication Server.

In addition to these terms we also use the following grouping terms:

ABAP or ABAP-only instance | An instance of type Central or Dialog or Abap_Scs.
ABAP+Java instance | An instance of type Central+Java or Dialog+Java.
Java or Java-only instance | An instance of type Java or Java_Scs.

For those SAP Systems that do not have a primary application server (i.e. a classical Central SAP Instance), Avantra chooses one to be considered central. This SAP Instance is performing the monitoring of the SAP System. It is flagged with a  icon.