MongoDB Documentation, Release 3.0.4 5.3.3 Database Profiler Output The database profiler captures data information about read and write operations, cursor operations, and database com- mands. To configure the database profile and set the thresholds for capturing profile data, see the Analyze Performance of Database Operations (page 227) section. The database profiler writes data in the system.profile (page 291) collection, which is a capped collection . To view the profiler’s output, use normal MongoDB queries on the system.profile (page 291) collection. Note: Because the database profiler writes data to the system.profile (page 291) collection in a database, the profiler will profile some write activity, even for databases that are otherwise read-only. The documents in the system.profile (page 291) collection have the following form. This example document reflects an insert operation: { "op" : "insert", "ns" : "test.orders", "query" : { "_id" : 1, "cust_id" : "A123", "amount" : 500, "status" : "A" }, "ninserted" : 1, "keyUpdates" : 0, "writeConflicts" : 0, "numYield" : 0, "locks" : { "Global" : { "acquireCount" : { "w" : NumberLong(1) } }, "MMAPV1Journal" : { "acquireCount" : { "w" : NumberLong(2) } }, "Database" : { "acquireCount" : { "w" : NumberLong(1) } }, "Collection" : { "acquireCount" : { "W" : NumberLong(1) } } }, , "millis" : 0, "execStats" : { }, "ts" : ISODate("2012-12-10T19:31:28.977Z"), Chapter 5. Administration 292 Example system.profile Document