[DOCS-8380] Add documentation on "Metadata Locks" Created: 19/Jul/16  Updated: 30/Oct/23

Status: Closed
Project: Documentation
Component/s: manual
Affects Version/s: None
Fix Version/s: Server_Docs_20231030

Type: Improvement Priority: Minor - P4
Reporter: Mark Brinsmead Assignee: Unassigned
Resolution: Won't Do Votes: 7
Labels: None
Remaining Estimate: Not Specified
Time Spent: Not Specified
Original Estimate: Not Specified

Issue Links:
Related
Participants:
Days since reply: 1 year, 14 weeks, 2 days ago
Epic Link: DOCSP-1769

 Description   

The output for db.currentOp() includes information for a class of locks named "Metadata".

The documentation describes these circularly as:

Metadata Represents metadata lock.

More information on metadata locks, their meaning, and their implications, would be helpful.



 Comments   
Comment by Education Bot [ 31/Oct/22 ]

Hello! This ticket has been closed due to inactivity. If you believe this ticket is still important, please reopen it and leave a comment to explain why. Thank you!

Comment by zhihui fan [ 03/Nov/16 ]

it would be good that we can know what does it means.

I see one of our slow query which Metadata.timeAcquiringMicros.W ~= total execution time, but has no idea about what it is.

2016-11-02T23:29:15.857-0700 I WRITE [conn615] update hwkemailimage.imagedata query:

{ _id: "2039171454_1478154555110" }

update: { _id: "2039171454_1478154555110", image:

{ 2: BinData(0, FFD8FFE000104A46494600010200000100010000FFDB00430006040506050406060506070706080A100A0A09090A140E0F0C1017141818171416161A1D251F1A1B231C161620...), 1: BinData(0, FFD8FFE000104A46494600010200000100010000FFDB00430006040506050406060506070706080A100A0A09090A140E0F0C1017141818171416161A1D251F1A1B231C161620...) }

, metadata:

{ 2: null, 1: null }

, created: new Date(1478154555110) } nscanned:0 nscannedObjects:0 nMatched:1 nModified:1 upsert:1 keyUpdates:0 writeConflicts:0 numYields:0 locks:{ Global: { acquireCount:

{ r: 2, w: 2 }

}, Database: { acquireCount:

{ w: 2 }

}, Collection: { acquireCount:

{ w: 1 }

}, Metadata: { acquireCount:

{ W: 1 }

, acquireWaitCount:

{ W: 1 }

, timeAcquiringMicros:

{ W: 724086 }

}, oplog: { acquireCount:

{ w: 1 }

} } 724ms

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