What is the default write concern in MongoDB?
majority
{ w: “majority” } is the default write concern for most MongoDB deployments.
What is MongoDB Read Write concern?
. MongoDB. read concern. allows you to control the consistency and isolation properties of the data read from replica sets and replica set shards.
Which of the following MongoDB write concerns enforce strongest data durability per operation?
Default Majority Write Concern: Providing Stronger Durability Guarantees “Out of the Box” MongoDB has always provided developers with the flexibility to control the desired levels of write durability, enabling them to balance latency and throughput against the application’s SLAs.
What is the syntax to create a database in MongoDB?
Create a New Database : You can create a new Database in MongoDB by using “use Database_Name” command. The command creates a new database if it doesn’t exist, otherwise, it will return the existing database. you can run this command in mongo shell to create a new database.
What is journaling in MongoDB?
With journaling enabled, MongoDB writes the in-memory changes first to on-disk journal files. If MongoDB should terminate or encounter an error before committing the changes to the data files, MongoDB can use the journal files to apply the write operation to the data files and maintain a consistent state.
What is read Concern majority?
“majority” For read operations not associated with multi-document transactions, read concern “majority” guarantees that the data read has been acknowledged by a majority of the replica set members (i.e. the documents read are durable and guaranteed not to roll back).
How does MongoDB write work?
MongoDB writes the in-memory changes first to the on-disk journal files. If MongoDB should terminate or encounter an error before committing the changes to the data files, MongoDB can use the journal files to apply the write operation to the data files.
How many writes per second can MongoDB handle?
Performance Scale After evaluating multiple technology options, AHL used MongoDB to replace its relational and specialised ‘tick’ databases. MongoDB supports 250 million ticks per second, at 40x lower cost than the legacy technologies it replaced.
What is db in MongoDB command?
MongoDB use DATABASE_NAME is used to create database. The command will create a new database if it doesn’t exist, otherwise it will return the existing database.
How does MongoDB write data?
MongoDB uses write ahead logging to an on-disk journal to guarantee write operation durability. The WiredTiger storage engine does not require journaling to guarantee a consistent state after a crash. The database will be restored to the last consistent checkpoint during recovery.
What is replica set and sharding?
What is the difference between replication and sharding? Replication: The primary server node copies data onto secondary server nodes. This can help increase data availability and act as a backup, in case if the primary server fails. Sharding: Handles horizontal scaling across servers using a shard key.
What is replication set?
A ReplicaSet’s purpose is to maintain a stable set of replica Pods running at any given time. As such, it is often used to guarantee the availability of a specified number of identical Pods.
What is read concern?
Read concern is a query option for replica sets. By default the read concern is local. This returns the most recent data available at the time of the query execution. The data may not have been persisted to the majority of the replica set members and may be rolled back.
What is read preference in MongoDB?
Read preference describes how MongoDB clients route read operations to the members of a replica set. click to enlarge. By default, an application directs its read operations to the primary member in a replica set (i.e. read preference mode “primary”).
In which directory does MongoDB write data by default?
/data/db
The default dbpath for mongodb is /data/db .