active proxy also has problem in following case.

1. host A is monitored via proxy, and it is maintenance status(nodata).

normally proxy collect data from host A, and send data to Zabbix server.
Zabbix server doesn't store the data while host A is maintenance mode.

2. network failure is occurred between Zabbix server and Zabbix proxy

Zabbix proxy continue to collect data from host A, but it can not send the data to Zabbix server.
Proxy keeps the data in its own database.

3. the network failure is recovered after maintenance period

Zabbix proxy send Zabbix server collected data include "the data while maintenance period"
Zabbix server store the all data (include maintenance period data).

I can also report that active proxies continue to try collecting data for hosts in maintenance mode with no data collection, at least in 2.0.2 (can someone test in 2.0.4?). The server doesn't appear to receive and store such data (it doesn't update in Latest data), but it seems quite pointless for the proxies to continue performing the collection.

My way of determining this is to enable maintenance mode with no data collection for a given test host, give time for the active proxy to request and receive the updated configuration, then stop the agent on the test host and watch the proxy's log - the proxy starts complaining about network errors when trying to get data for agent items from the test host. Meanwhile if I try the same test for a host monitored directly by the server (no proxy) and watch the server's log instead, there are no such messages in the server log.

just collecting of the data by active proxies is ok - they update config once an hour by default, and maintenance periods could change during that time. the scenario kodai described is a bug, though

Hello,

No update ? No data maintenance has no action on data collection on proxy, So "unreachable processes" of proxyes are used for nothing in this case.