Here is a summary of the directives available in the settings sub-document:
| Directive | Data Type | Notes |
| chainingAllowed | Boolean | Set this value to false if you wish secondary replica set members to replicate only from the primary. The default value is true, meaning secondaries can update each other, referred to as chained replication. |
| heartbeatIntervalMillis | Integer | This value is set internally. |
| heartbeatTimeoutSecs | Integer | The number of seconds allowed without receiving a heartbeat before a replica set member is considered unreachable. The default value is 10. |
| electionTimeoutMillis | Integer | The number of milliseconds allowed to elapse without receiving a heartbeat before an election is called. This only applies to members using protocolVersion set to 1. The default value is 10000 (that is, 10 seconds). Set this value high if you have frequent communication interruptions between replica set members (and fix the communication problems... |
