Locking the whole Data base if -1 see code????

//contains locked records
private Vector r_lock = new Vector(); //Global declaration
public void lock(int record) throws IOException {
synchronized(r_lock)
{
while(r_lock.contains(new Integer(record)))
{
try
{
wait();
}
catch(InterruptedException e)
{
throw new IOException("lock failed");
}
}
r_lock.add(new Integer(record));
}

}
/**
* Unlock the requested record. Ignored if the caller does not have
* a current lock on the requested record.The record that was locked
* is removed from the Vector r_lock and all threads are notifyed.
*/
public void unlock(int record) {
synchronized(r_lock)
{
if(r_lock.contains(new Integer(record)))
{
r_lock.remove(new Integer(record));
}
r_lock.notifyAll();
}
}
Now My question is how to lock the whole database if -1??? and then how to unlock it
Thanks Lisa

How about modifying your lock code in this fashion:
while((r_lock.contains(new Integer(record))) | | (r_lock.contains(new Integer(-1))))
You shouldn't have to change your unlocking code.

Thanks Alot if I do this as you mention above will it lock the whole Database???

Thanks Lisa

Hi Lisa,
Vectors are by default synchronised objects and again your code synchronises on the vector object is it OK?
Is it not a overhead ??
Bye,
Lokesh

Adding the second condition to your while statement prevents any threads from continuing as long as r_lock contains -1, no matter which record they are trying to lock.

Thanks Very much I see the logic now. If you never unlock -1 no other threads can get in essentially blocking until you reboot.
Thanks Lisa

Originally posted by Lisa Foster:
//contains locked records
private Vector r_lock = new Vector(); //Global declaration
public void lock(int record) throws IOException {
synchronized(r_lock)
{
while(r_lock.contains(new Integer(record)))
{
try
{
wait();
}
catch(InterruptedException e)
{
throw new IOException("lock failed");
}
}
r_lock.add(new Integer(record));
}

}
/**
* Unlock the requested record. Ignored if the caller does not have
* a current lock on the requested record.The record that was locked
* is removed from the Vector r_lock and all threads are notifyed.
*/
public void unlock(int record) {
synchronized(r_lock)
{
if(r_lock.contains(new Integer(record)))
{
r_lock.remove(new Integer(record));
}
r_lock.notifyAll();
}
}
Now My question is how to lock the whole database if -1??? and then how to unlock it
Thanks Lisa

i think should
use r_lock.wait()
and r_lock.notifyAll()
cos r_lock was synchorinized but not this.

Have you considered blockinh the thread that gets the 'database lock' until all the threads updating records have finished with their locks? - If you do not then the DB lock thread can potentially corrupt a record to which another thread thinks that it has exclusive access
Any thoughts?
Conor

I agree with Conor.
One solution may be to use a flag to indicate that a client wants a full lock, which prevents any new locks. Once all the current locks are released, the client can obtain the full lock.

OR ....
Once a full db lock is granted then block in the lock method until all outstanding locks have been released ....