What is the Oplog in MongoDB?

What is the Oplog in MongoDB?

The Oplog (operations log) is a special capped collection that keeps a rolling record of all operations that modify the data stored in your databases. MongoDB applies database operations on the primary and then records the operations on the primary’s oplog.

What is capped collection in MongoDB?

Capped collections are fixed-size collections that support high-throughput operations that insert and retrieve documents based on insertion order.

Where is Oplog in MongoDB?

Oplog is stored in local DB as oplog.rs collection. This is a capped collection but can be tailed using a cursor. In Python, pymongo package can be used to connect to MongoDB and tail the oplog.

What are the characteristics of capped collection in MongoDB?

The capped collection will restrict the update when the update result reaches the document size. The capped collection will store the documents in the order of disk storage. When the max limit is exceeded, then insertion and updation are not allowed on capped collection.

What is Oplog size in MongoDB?

192 MB of free disk space. In most cases, the default oplog size is sufficient. For example, if an oplog is 5% of free disk space and fills up in 24 hours of operations, then secondaries can stop copying entries from the oplog for up to 24 hours without becoming too stale to continue replicating.

Where is Oplog size in MongoDB?

To view the current size of the oplog, switch to the local database and run db. collection. stats() against the oplog.rs collection. stats() displays the oplog size as maxSize .

Which of the following is a capped collection?

3. Which of the following collection is capped? Explanation: The database profiler writes data in the system. profile collection, which is a capped collection.

What type of management do capped collections provide for inserted documents in MongoDB?

Discussion Forum

Que. Capped collections provide __________ management of inserted documents in MongoDB.
c. LRU
d. MRU

What is the risk of having a small Oplog?

Risks with the oplog are related to its being capped: if your oplog is too small, any maintenance operations that require you to take down a replica can cause the copy to fail.

How do I enable Oplog?

How to enable the oplog on Ubuntu MongoDB for Meteor 15 Aug 2016

  1. Enable oplog. In /etc/mongodb.conf , add replSet = rs0.
  2. Add a user to access the oplog. Switch to the admin database with: rs0:PRIMARY> use admin.
  3. Tweak your Meteor config to use the oplog.
  4. Restart your Meteor application.
  5. Confirm that the oplog is being used.

Which of the following is correct about MongoDB?

6. Which of the following true about mongoDB? Explanation: MongoDB is a cross-platform, document oriented database that provides, high performance, high availability, and easy scalability.

What is the maximum size of collection in MongoDB?

Sharding Operational Restrictions

Average Size of Shard Key Values 512 bytes 256 bytes
Maximum Number of Splits 32,768 65,536
Max Collection Size (64 MB Chunk Size) 1 TB 2 TB
Max Collection Size (128 MB Chunk Size) 2 TB 4 TB
Max Collection Size (256 MB Chunk Size) 4 TB 8 TB


Back to Top