Low-Memory Situations
IfWeb Server must run in low-memory situations, reduce the thread limit to a bare minimum
bylowering the value of the Maximum Threads setting on the conguration's Performance Tab
⇒HTTPsub tab. You can also set it with wadm set-thread-pool-prop command's
max-threadsproperty.
Yourweb applications running under stress might sometimes result in the server running out
ofJava VM runtime heap space, as can be seen by java.lang.OutOfMemoryError messages in
theserver log le. There could be several reasons for this (such as excessive allocation of
objects),but such behavior could aect performance. To address this problem, prole the
application.Refer to the following HotSpot VM performance FAQfor tips on proling
allocations(objects and their sizes) of your application:
http://java.sun.com/docs/hotspot/index.html
Attimes your application could be running out of maximum sessions (as evidenced by a “too
manyactive sessions” message in the server log le), which would result in the container
throwingexceptions, which in turn impacts application performance. Consideration of session
managerproperties, session creation activity (note that JSPs have sessions enabled by default),
andsession idle time is needed to address this situation.
TooFew Threads
Theserver does not allow the number of active threads to exceed the thread limit value. If the
numberof simultaneous requests reaches that limit, the server stops servicing new connections
untilthe old connections are freed up. This can lead to increased response time.
InWeb Server, the server’s default maximum threads setting is 128. Ifyou want your server to
processmore requests concurrently, you need to increase the maximum number of threads.
Thesymptom of a server with too few threads is a long response time. Making a request from a
browserestablishes a connection fairly quickly to the server, but if there are too few threads on
theserver it might take a long time before the response comes back to the client.
Thebest way to tell if your server is being throttled by too few threads is to see if the number of
activesessions is close to, or equal to, the maximum number of threads. To do this, see “Session
Creation(Thread) Information” on page 57.
Low-MemorySituations
SunJavaSystem Web Server 7.0 Update 1 Performance Tuning,Sizing, and Scaling Guide •86