For performance reasons, a node running the MTA keeps a cache of channel counters in memory using a shared memory section (UNIX) or shared file-mapping object (NT). As processes on the node enqueue and dequeue messages, they update the counters in this in-memory cache. If the in-memory section does not exist when a channel runs, the section will be created automatically. (The imta start command also creates the in-memory section, if it does not exist.)
The command imta counters -clear or the imta qm command counters clear may be used to reset the counters to zero.