Understanding garbage collector output

Question

Hi all.
My application uses an increasing amount of memory, and in order to solve the problem I have turned on the -verbosegc option. The output is as follows:
<GC: managing allocation failure: need 1040 bytes, type=1, action=1>
<GC: 504 milliseconds since last GC>
<GC: freed 6530 objects, 288432 bytes in 10 ms, 35% free (661616/1887424)>
  <GC: init&scan: 1 ms, scan handles: 7 ms, sweep: 2 ms, compact: 0 ms>
  <GC: 4 register-marked objects, 7 stack-marked objects>
  <GC: 8 register-marked handles, 136 stack-marked handles>
  <GC: refs: soft 0 (age >= 32), weak 0, final 1, phantom 0>
<GC: managing allocation failure: need 1040 bytes, type=1, action=2>
<GC: 10 milliseconds since last GC>
<GC: expanded object space by 1048576 to 2936000 bytes, 58% free>
<GC: need to expand mark bits to cover 2560 bytes>Is any one able to explain this output for me? My problem is that the object space is expanded regularly and eventually the garbage collector writes "totally out of heap space" and an OutOfMemoryError occurs.
My -version is
java version "1.3.0"
Java(TM) 2 Runtime Environment, Standard Edition
Classic VM (build 1.3.0-1, native threads, jit)running on UNIX, Digital Alpha.
Regards,
Torben Lange

Answer 1

Just a follow up on my memory leak problem which I have solved now.
I had created a class which handles database connections. The constructor looked something like this:
Connection connection;
public DBConnection() {
  DriverManager.registerdriver(new myDriver());
  connection = DriverManager.getConnection(...);
}My application creates an object of this class, uses it and then closes the object. This goes on all the time. (Yes, it could be handled another way by pooling database access or simply keep the connection open without closing it - but it isn't.)
It seems that the registration of the driver in the constructor eventually will fill the memory - apparently the same driver is registered several times.
Problem was solved when changing the code into the following:Connection connection;
static boolean isRegistered = false;
public DBConnection() {
  if (! isRegistered) {
    DriverManager.registerdriver(new myDriver());
    isRegistered = true;
  connection = DriverManager.getConnection(...);
}Hope this could help others in the same situation.
Regards,
Torben Poort Lange