In normal case when I have problem with db - zabbix inform in log level 3 but not in this case.

I have problem with tablespace of History and zabbix server cant write history to DB and it history buffer is full.

When buffer is full the zabbix server process is still running (don't die) but also dont log anything. You can only see there is a problem on web gui or get some random alerts from agents that they are not available.

When I switch to log lever 4 and restart server it , after a while i can see in log such lines:

14700:20121113:204218.888 History buffer is full. Sleeping for 1 second.
14665:20121113:204218.888 In DCvacuum_history() history_gap_num:0/116508
14665:20121113:204218.888 End of DCvacuum_history()

IMHO it should log "History buffer is full." on all levers of logging maybe also send email to zabbix admins like DB problems appear.