I have error when I would like to read from Cassandr:
WARN 19:17:29,839 Heap is 0.8888050654459693 full.  
    You may need to reduce memtable and/or cache sizes.  
    Cassandra will now flush up to the two largest memtables to free up memory.  
    Adjust flush_largest_memtables_at threshold in cassandra.yaml if you don't want Cassandra to do this automatically 
INFO 19:17:30,238 Unable to reduce heap usage since there are no dirty column families
When I reduce flush_largest_memtables_at threshold, nothing changes so can you help me to reduce memtable or caches sizes because I don't know how do this.