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. All the replica set members contain a copy of the

Question

Options

• A<replicasetid>.oplog.rs
• Boplog.rs
• C<database>..oplog.rs
• Dlocal.oplog.rs

• A
  4% (2)
• B
  2% (1)
• C
  2% (1)
• D
  93% (50)

Explanation

In MongoDB replica sets, the oplog is stored in the local database as a capped collection named oplog.rs, making local.oplog.rs the correct and complete namespace. Option A is wrong because the collection name doesn't include the replica set ID - MongoDB uses a fixed name regardless of your replica set configuration. Option B (oplog.rs alone) omits the required database prefix; every MongoDB collection must be referenced as database.collection. Option C is wrong because the oplog is not stored per-database - it lives in one centralized location (local) and captures operations across all databases. Memory tip: Think "Local Oplog" - the local database is a special system database that exists on every mongod instance, and it's the home for replication metadata; nothing user-facing lives there, which is why it's easy to overlook.

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