fsyncUnlock

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Definition

  • fsyncUnlock
    • Reduces the lock taken by fsync (with the lock option) on a mongod instance by 1.

Important

The fsync lock and fsyncUnlock operations maintain a lock count. Each fsync lock operation increments the lock count, and fsyncUnlock decrements the lock count.

To unlock a mongod instance for writes, the lock count must be zero. That is, for a given number of fsync lock operations, you must issue a corresponding number of fsyncUnlock operations to unlock the instance for writes.

fsyncUnlock is an administrative operation. Typically you will use fsyncUnlock following a database backup operation.

To run the fsyncUnlock command, use the db.adminCommand() method:

db.adminCommand( { fsyncUnlock: 1 } )

The operation returns a document with the following fields:

infoInformation on the status of the operation
lockCount ( New in version 3.4 )The number of locks remaining on the instance after the operation.
okThe status code.

Tip

The mongo shell provides the helper method db.fsyncUnlock().

Examples

Consider a situation where db.fsyncLock() has been issued two times. The following fsyncUnlock operation reduces the locks taken by db.fsyncLock() by 1:

db.adminCommand( { fsyncUnlock: 1 } )

The operation returns the following document:

{ "info" : "fsyncUnlock completed", "lockCount" : NumberLong(1), "ok" : 1 }

As the lockCount is greater than 0, the mongod instance is locked against writes. To unlock the instance for writes, run the unlock operation again:

db.adminCommand( { fsyncUnlock: 1 } )

The operation returns the following document:

{ "info" : "fsyncUnlock completed", "lockCount" : NumberLong(0), "ok" : 1 }

The mongod instance is unlocked for writes.