Q :- What is Queuing Theory ?
A :- The primary tool for studying the problem of congestion is known as Queueing Theory. Any system in which arrivals place a demand upon a finite capacity, a limited space or limited resources may be termed a Queueing System. Queueing Theory is a branch of statistics which deals with arrival times of people (or transport) and service rates (time taken for change, or buying something, tickets, gates, etc).
Q :-Definition of a system hang or what may look like a hang ?
A :- The process is still present but is not responding in some sence. A hang may look like a) Deadlock (halt), b) Infinite loop, c) Resource contention
Q :- Is there any Difference between heap dumps, core dumps, thread dumps, memory dumps, java dumps, jvm dumps? what is use these things when and how to take these dumps ? what processes are available other than kill -3 pid? are there any tools that track these dumps? what can be inferred from the dumps analysis? how to take these dumps when a server fails and pid no more available?
A:-
1. Thread dump - These are taken to understand what threads are doing in JVM at any given point in time. It is done by sending ctrl+pause / kill -QUIT <pid>. This signal is handled by JVM and it dumps the thread information alnog with stack. This is mainly done to understand stuck threads, waiting threads, running threads and other such information. Sometimes lock information can also be obtained from this. But since JDK 1.5, lock information is getting tricker with threaddumps.
2. Core Dump/Heap Dump - When JVM exits, there is a high probability that it would create a core dump/heap dump in the directory. This is nothing but the heap representation of JVM. It can be opened easily with JProfiler, Yourkit etc and if JVM crashed due to memory leaks, this dump would be of great importance.
3. When no pid is available, its not possible to get the thread dump. no pid means that the process is not running...isnt that the case. :)
4. threads - The number of threads in the pool. Thread count should give you the current threads in the thread pool. Thread pool is nothing but a way of maintain a set of threasd so that it can be assigned whenever required (instead of creating a thread for every request which is time consuming and expensive).
A :- The primary tool for studying the problem of congestion is known as Queueing Theory. Any system in which arrivals place a demand upon a finite capacity, a limited space or limited resources may be termed a Queueing System. Queueing Theory is a branch of statistics which deals with arrival times of people (or transport) and service rates (time taken for change, or buying something, tickets, gates, etc).
Q :-Definition of a system hang or what may look like a hang ?
A :- The process is still present but is not responding in some sence. A hang may look like a) Deadlock (halt), b) Infinite loop, c) Resource contention
Q :- Is there any Difference between heap dumps, core dumps, thread dumps, memory dumps, java dumps, jvm dumps? what is use these things when and how to take these dumps ? what processes are available other than kill -3 pid? are there any tools that track these dumps? what can be inferred from the dumps analysis? how to take these dumps when a server fails and pid no more available?
A:-
1. Thread dump - These are taken to understand what threads are doing in JVM at any given point in time. It is done by sending ctrl+pause / kill -QUIT <pid>. This signal is handled by JVM and it dumps the thread information alnog with stack. This is mainly done to understand stuck threads, waiting threads, running threads and other such information. Sometimes lock information can also be obtained from this. But since JDK 1.5, lock information is getting tricker with threaddumps.
2. Core Dump/Heap Dump - When JVM exits, there is a high probability that it would create a core dump/heap dump in the directory. This is nothing but the heap representation of JVM. It can be opened easily with JProfiler, Yourkit etc and if JVM crashed due to memory leaks, this dump would be of great importance.
3. When no pid is available, its not possible to get the thread dump. no pid means that the process is not running...isnt that the case. :)
4. threads - The number of threads in the pool. Thread count should give you the current threads in the thread pool. Thread pool is nothing but a way of maintain a set of threasd so that it can be assigned whenever required (instead of creating a thread for every request which is time consuming and expensive).
