Interactive Reports for Java Systems - Performance

From the point of view of the end user, response times are one of the most important criteria for the performance of systems and databases. In the context of interactive reporting, there are four reports that give you a quick overview of the development of these metrics and their relationship over time for Java systems:

Threads ( <System ID> – SAP J2EE ENGINE <Release> Performance Threads )
The report shows the load of the system and application threads. The value is displayed as the mean value of all nodes in the selected system, and as the mean value of the node with the highest load. System threads are SAP J2EE Engine processes, which perform operations of the engine itself, whereas application code is performed in application threads. Both threads have profile parameters that specify the maximum number of processes that the system provides in the respective thread pool. More information: Thread System. The load displayed is the percentage of the maximal possible number of threads which are active.

You also have the following options in the report:
- You can restrict the thread load to be displayed, by host, instance or node, in the Overview, in the screen areas Filter Hosts, Filter Instances, and Filter Nodes.
- The Detail view shows the load of the ten nodes in the displayed system, which have the highest load for the application and system threads. You can filter by host and instance. You can determine the thread load distribution, as well as the absolute load.
Garbage Collection ( <system ID> – SAP J2EE ENGINE <release> Performance Garbage Collection )
The report shows the system load of garbage collection. During garbage collection (GC), the Java Virtual Machine cannot perform other tasks, such as user requests. GC therefore directly affects system performance, and increased GC load indicates other performance problems. For more information, see How the Local Garbage Collector Works.

We distinguish between a minor garbage collection, in which no longer required objects are removed from new space, and a full garbage collection, in which no longer required objects are removed from old space. A full garbage collection starts when old space is full. As old space is much bigger than new space, a full garbage collection takes much longer, and is more performance-critical. For more information about the different memory areas of the Java Heap, see Interactive Reports für Java Systems - Usage in the description of the Old Space Usage report.

The report shows the following key figures:
- The report shows the proportion of all garbage collections in the total runtime of the Java processes, both the mean value in the displayed period, and the maximum hourly mean value within the period. The mean value should not be more than 5% of the total runtime.
- The proportion of full garbage collections is displayed. This value should be under 5%.
- You can further restrict these key figures by host, instance or node, in der Overview in the screen areas Filter Hosts, Filter Instances, and Filter Nodes.
- These key figures of the system displayed are output at node level, in the Detail View. The values of the ten nodes for which these two proportions are highest, are displayed. You can also filter here by host and instance, to localize a problem.
Response Times ( <system ID> – SAP J2EE ENGINE <release> Performance Response Times )
The report shows the most important AS Java response times, as follows:
- JCo Calls
  The SAP Java Connector (SAP JCo) is a component that supports communication between AS ABAP and AS Java, in both directions.
- Servlets
  Servlets are Java classes whose instances receive and answer user queries. The key figure is a user response time, that is, how long the user must wait for the resolution of his or her query.
- SQL Statements
  This response time is how long the database took to respond to queries received.
- Web Dynpro Applications
  This key figure is the user response time of Web Dynpro applications.
Note
Servlet, and their special case Web Dynpro Applications response times, are from the user perspective, while the response times of JCo calls and SQL statements are part of the total response time, which can help to identify performance bottlenecks when handling problems.

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You also have the following options in the report:
- Restrict the response times to be displayed by hosts, instances or nodes, in the Overview, in the screen areas Filter Hosts, Filter Instances, and Filter Nodes.
- The response times of the ten nodes in the selected system for which the response time is longest, are shown in the Detail view. You can specify on which of the 4 response times the graphic is based. You can also filter by host and instance here.
Old Space Usage ( <system ID> – SAP J2EE SYSTEM <release> Usage Old Space Usage )
The report shows the percentage use of effective old space.

The Java heap (the memory space in which the Java objects of a Java virtual machine are created) is divided into new space and old space (or young and old generation). The new space is the memory space in which new Java objects are created. Objects which have survived a specified number of garbage collections (GC), are moved into old space.

The effective old space is the proportion of the old space which triggers a full garbage collection, if it is full. The effective old space is the old space minus the new space, because a full garbage collection starts when old space no longer has enough free space for the objects moved from new space by a minor garbage collection.

The use of effective old space is in the form of a saw-tooth, because each minor GC moves objects into old space (increasing its use), but no longer required objects are only removed from old space by a full GC, much less often. This profile shows you the effectiveness of the full GC.

Note
The use of effective old space can be over 100%, if the entire old space is occupied by objects.

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You also have the following options in the report:
- You can restrict the usage to be displayed, by host, instance or node, in the overview in the screen areas Filter Hosts, Filter Instances, and Filter Nodes.
- The load of the ten nodes of the selected system with the highest load, is shown in the Detail view. You can also filter by host and instance here.
Memory Allocation ( <system ID> – SAP J2EE SYSTEM <release> Usage Memory Usage )
This report shows the rate of memory assignment in new and old space of the Java heap, in bytes per second. The allocation rate is the rate of memory allocation for the creation of new objects in new space; the promotion rate is the rate of memory allocation for moving (promoting) objects from new space into old space. The latter occurs in minor garbage collections.

You can restrict the assignment rates, by host, instance or node, in the screen areas Filter Hosts, Filter Instances, and Filter Nodes.
Database Performance ( <system ID> – SAP J2EE ENGINE <release> Performance DB Performance )
This report outputs the response time per SQL statement ands the number of SQL statements, to give you an overview of the performance and use of the database.

Note Note

For information about how you can specify the desired systems and the time interval to be displayed, and how to call interactive reporting, see Using Interactive Reporting.
For information about the different display options for the reports for Java systems with regard to metrics, threshold values, and instances, see Interactive Reports for Java Systems.

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