We run a resync on SECONDARY on a prod replica. During the process, oplog on secondary was set to 131GB by mongo where as the PRIMARY oplog is only 3GB.

SECONDARY oplog
erep:RECOVERING> db.printReplicationInfo()
configured oplog size: 134152.873828125MB
log length start to end: 0secs (0hrs)
oplog first event time: Wed Jul 09 2014 09:12:53 GMT-0600 (MDT)
oplog last event time: Wed Jul 09 2014 09:12:53 GMT-0600 (MDT)
now: Thu Jul 10 2014 06:45:30 GMT-0600 (MDT)

PRIMARY Oplog

erep:PRIMARY> db.printReplicationInfo()
configured oplog size: 3181.0236328125MB
log length start to end: 56786secs (15.77hrs)
oplog first event time: Wed Jul 09 2014 14:57:31 GMT-0600 (MDT)
oplog last event time: Thu Jul 10 2014 06:43:57 GMT-0600 (MDT)
now: Thu Jul 10 2014 06:44:10 GMT-0600 (MDT)

erep:RECOVERING> rs.status()
{
"set" : "erep",
"date" : ISODate("2014-07-10T15:33:17Z"),
"myState" : 3,
"members" : [
{
"_id" : 0,
"name" : "wslermdb01sp:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 87654,
"optime" :

{ "t" : 1405006395, "i" : 9 }

,
"optimeDate" : ISODate("2014-07-10T15:33:15Z"),
"lastHeartbeat" : ISODate("2014-07-10T15:33:17Z"),
"lastHeartbeatRecv" : ISODate("1970-01-01T00:00:00Z"),
"pingMs" : 2
},

{ "_id" : 2, "name" : "wslerudh01sp:27017", "health" : 1, "state" : 7, "stateStr" : "ARBITER", "uptime" : 87654, "lastHeartbeat" : ISODate("2014-07-10T15:33:16Z"), "lastHeartbeatRecv" : ISODate("1970-01-01T00:00:00Z"), "pingMs" : 1 }

,
{
"_id" : 3,
"name" : "wslermdb02sp:27017",
"health" : 1,
"state" : 3,
"stateStr" : "RECOVERING",
"uptime" : 94556,
"optime" :

{ "t" : 1404918773, "i" : 1 }

,
"optimeDate" : ISODate("2014-07-09T15:12:53Z"),
"self" : true
}
],
"ok" : 1
}

Question: what is the max oplog size we can use for both and should I make them both 131GB or go higher?