[Serusers] UA records are lost while UA is still online

[szj]

Hi:

  I use the latest code from SER cvs. the mysql db and ser are located
on two computer. I registered 3 sip UA on the registrar which alse is
a proxy. all the ua will expire after 1 hour. But after a while, i don't
know how long it is. I found the location table has lost the ua record.
my three sip ua is still online.
  I wonder whether the registrar and usrloc have other condition I
don't know. What happens to them??
  Thanks for your  advice and help!
   Best Regards

  Sun Zongjun