I run into a problem quite often where I need to re-arrange which hosts are monitored by proxies in my environment. Here's my scenario:

1. At times a Zabbix Proxy will go offline for some reason (Proxy "A") (network/hardware issues/etc.)
2. Proxy A will have data that it wasn't able to send before it went down.
3. While Proxy A is down, I change the hosts that were monitored by it to be monitored by a different proxy (Proxy B).
4. Proxy A comes back online within 30 minutes and syncs it's configuration with the Zabbix Server.
5. Proxy A sees that it is no longer configured to monitor the hosts it had before and deletes all historical data related to them.

In this particular case, I want Proxy A to still send the information it had collected BEFORE the configuration was changed. That way I don't lose data for hosts simply because I wanted to continue monitoring them from somewhere else.

I am not referring to cases where data is older than the cache time allows.