In db.currentOp () “op”: “getmore” what does it mean

  mongodb, question

I run db.currentOp () on the mongodb command line and “op” appears in the returned result: “getmore”,, what is getmore? And it is particularly time consuming:

>db.currentOp()
 {
 "inprog" : [
 {
 "opid" : 821006778,
 "active" : true,
 "secs_running" : 0,
 "microsecs_running" : NumberLong(252939),
 "op" : "getmore",
 "ns" : "local.oplog.$main",
 "query" : {
 
 },
 "client" : "10.171.53.62:34632",
 "desc" : "conn9912",
 "threadId" : "0x7f9665e39700",
 "connectionId" : 9912,
 "waitingForLock" : false,
 "numYields" : 0,
 "lockStats" : {
 "timeLockedMicros" : {
 "r" : NumberLong(14),
 "w" : NumberLong(0)
 },
 "timeAcquiringMicros" : {
 "r" : NumberLong(1),
 "w" : NumberLong(0)
 }
 }
 }
 ]
 }

getmoreIt takes data from a cursor. If you encounter problems, you can ask Google first, then you have to learn to climb over the wall first.
The more data you have, the more time it takes, which is normal. The data you provided is the system pulling data from the oplog and distributing it to the slave nodes, which looks like master/slave replication.
Oplog table is a large table without index by default, so it will take a long time to traverse for the first time.