This value is used to protect you from accidentally dropping data from SiriDB. The threshold is a value between 0 and 1 (0/100%). The threshold value is only checked against the pool receiving your query. The default threshold value is 1 (100%) but it might be a good idea to change this to a lower value.
Note
Currently the drop_threshold is only used for dropping series and shards because these are the only queries where we allow to drop multiple entries at once.
# Do not allow dropping more than 10% series or shards at once
alter database set drop_threshold 0.1
# View the current threshold
show drop_threshold