[otrs] Ticket::NumberGenerator, clearing database

[Tom]

Hello 

I'm new one to OTRS 
and I try to SET best configuration for me .

I use OTRS2 2.0.4p01-17 on debian.


I want to set Ticket::NumberGenerator: to AutoIncrement.
Now for Ticket::NumberGenerator I have DateChecksum under WEB  SysConfig. When I change to AutoIncrement there is problem with fetching new emails and I have such notice in system log when system try to fetch email through PostMasterPOP3:

"Can't create PID PostMasterPOP3, because it's already running (xxxxxxxxxxxxxx/9287)! "

When I run PostMasterPOP3.pl with force otpion under console there I have error in AutoIncrement.pl script: 


"Quantifier follows nothing in regex; marked by <-- HERE in m/+ <-- HERE .{0,2}(10\d{5,10})/ at /usr/share/otrs/Kernel/System/Ticket/Number/AutoIncrement.pm line 110, <PRODUCT> line 4."



 Is this BUG or what? 

What is the problem, how to change Ticket::NumberGenerator ?


Which tables (mysql)  may I truncate to clear data such as fetched emails (attachements), ticket history, notes etc. ?
I mean truncate tables which collects data ivolved with fetched emails, I mean which tables truncate to reset OTRS (not to delete users,queues states,Salutations, notifications and other similar)? Reinstall of hole database is nedded I mean is this safe to truncate single tables?


What for are options when sending answer or new email ticket from OTRS:
Time units (work units)
Pending Date (for pending* states)
?




Thx in advance