I have an installation using usrloc + db_mode=1.

If I want on db_mode=1 or db_mode=2 the expired contacts to be cleaned up I have to enable the modparam db_timer_clean:

The docs say:

"Enable (1) or disable (0) cleaning of expired db records on timer basis for db_mode WRITE-BACK and WRITE-THROUGH. It uses the secondary timer process."

I have the following doubts:

1- What does the reference "it uses the secondary timer process" mean? Is there a specific secondary timer just for this purpose?

2- Is  #1 related to the modparam timer_procs? (so it uses one of those when enabled?)

3- Why/When would you need a timer_proces modparam with a value higher than "1"? 

Thanks, 

Joel.