How long is the OLT failover time?

Thanks Gavin.
" the ONT MAC address of OLT A will learned by OLT B uplink port", does it mean ONT mac addresses on core switch port will be learned by core switch port which is connected to OLT B uplink or OLT B uplink port? is this also include the users mac addresses?
Is it OLT B will know two entries of ONT mac address and user mac address from uplinks and PON ports?

simply to say ,if in the core switch do not configure port isolation , the switch will send ONT mac to another OLT , another OLT will be learned this MAC from uplink port (switch side ).

Thanks a lot Gavin. Last question, is the traffic from ONT sent out from splitter to both OLTs even if one OLT PON port is not active? How to verify whether ONT already configured to support type B & C dual homing?

huawei_B(protect-group-1)#protect-group member port 0/1/0 role protect
huawei_B(protect-group-1)#peer-group-member peer-node active peer-port 0/1/0
huawei_B(protect-group-1)#protect-group enable
huawei_B(protect-group-1)#uplink-monitor port 0/3/0
huawei_B(protect-group-1)#quit
huawei_B(config)#onu-switch notify ipv4 enable
huawei_B(config)#save

in the group , only one PON port in work state , So, the ONU will send to traffic to only one OLT . to verify the ONU in type B or type C to see the PON port or  ONU in which type protect group .

Thanks Gavin. Sorry, if configured port isolation on core switches, then how OLT A communicate with OLT B? OLT need to
monitor each other for confirm whether alive or not, right?

enable ARP proxy or configure route ，let them communicate via L3 not L2

Thanks Gavin. What are the default timers for OLT peer monitoring? How many seconds hello/keepalive time? How is the hold time and dead time? Thanks.