we found data collector services working fine but still it's stopped polling statistics in CAPM console. Many devices currently showing no data available also few interfaces are not listed in console end.
Data collectors heap was gowning and causing the Data Collectors to hang.
We found the following exception in the logs "ConcurrentModficationException", This was because there are 2 threads trying to modify the same IP in the IP Poll Error logging. This code was introduced in 20.2.7 and is not written to thread-safe after reviewing the code. This code will be updated to be thread safe. DE500583
Release : 20.2
Component : IM Polling
The fix for this issue is in 21.2 and the workaround for this issue is to downgrade the data collectors to 20.2.6.