MongoDB Documentation, Release 3.0.4 system.profile. numYield system.profile. locks • Global represents global lock. • MMAPV1Journal represents MMAPv1 storage engine specific lock to synchronize journal writes; for non-MMAPv1 storage engines, the mode for MMAPV1Journal is empty. • Database represents database lock. • Collection represents collection lock. • Metadata represents metadata lock. • oplog represents lock on the oplog . • R represents Shared (S) lock. • W represents Exclusive (X) lock. • r represents Intent Shared (IS) lock. • w represents Intent Exclusive (IX) lock. system.profile.locks. acquireCount system.profile.locks. acquireWaitCount system.profile.locks. timeAcquiringMicros system.profile.locks. deadlockCount system.profile. nreturned system.profile. responseLength • Projections (page 107) Number of times the operation had to wait for the acquireCount (page 295) lock acquisitions because the locks were held in a conflicting mode. acquireWaitCount (page 295) is less than or equal to acquireCount (page 295). Number of times the operation acquired the lock in the specified mode. The returned lock information for the various lock types include: Cumulative time in microseconds that the operation had to wait to acquire the locks. timeAcquiringMicros (page 295) divided by acquireWaitCount (page 295) gives an approxi- mate average wait time for the particular lock mode. Number of times the operation encountered deadlocks while waiting for lock acquisitions. For more information on lock modes, see What type of locking does MongoDB use? (page 758). The number of documents returned by the operation. The length in bytes of the operation’s result document. A large responseLength (page 295) can affect performance. To limit the size of the result document for a query operation, you can use any of the following: The possible locking modes for the lock types are as follows: The possible lock types are: The system.profile.locks (page 295) provides information for various lock types and lock modes (page 758) held during the operation. New in version 3.0.0: locks (page 295) replaces the lockStats field. The number of times the operation yielded to allow other operations to complete. Typically, operations yield when they need access to data that MongoDB has not yet fully read into memory. This allows other operations that have data in memory to complete while MongoDB reads in data for the yielding operation. For more information, see the FAQ on when operations yield (page 759). 295 5.3. Administration Reference