C100DBA Replication Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✗

  rs.status()

  Why it's wrong here

  rs.status() shows general replica set information and the state of each member, but it does not calculate or display the specific replication lag duration. It is useful for general monitoring, but for troubleshooting sync delays, more specialized commands are required to get the precise time-lag metrics.

• ✗

  rs.printReplicationInfo()

  Why it's wrong here

  rs.printReplicationInfo() displays the status and size of the oplog. It tells you the time range covered by the oplog, which is useful for capacity planning, but it does not tell you the current replication lag for each secondary node relative to the primary's latest operation.

• ✓

  rs.printSecondaryReplicationInfo()

  Why this is correct

  This specific shell helper calculates the difference between the primary's last operation and the secondary's applied operation, outputting the lag in seconds. It is the most effective command for quickly identifying which nodes are falling behind and verifying that the entire set is effectively synchronized.

• ✗

  db.stats()

  Why it's wrong here

  db.stats() provides statistics about a specific database, such as the number of collections, indexes, and total data size. It has no visibility into the replication status or the health of the replica set members. It is used for database-level capacity management rather than cluster health monitoring.