eG Help

Rollbacks are expensive operations and will have to be avoided at all costs. Using the MongoTransTest test, administrators can be instantly alerted if more than a permissible number of rollbacks are happening on a target MongoDB server. In addition, the test monitors transaction checkpoints. A checkpoint acts as a recovery point for an operation. When a transaction attempts to modify the data in a data file, MongoDB presents an in-memory snapshot/copy of that data and allows changes to be made to that data. While writing the data in the snapshots to the disk, MongoDB creates restoration points between the snapshots, called checkpoints. If these checkpoints are not created frequently, it only means that data is not written to the disk regularly; this increases the risk of data loss during recovery. To avoid this, administrators can use the MongoTransTest test to monitor the time taken for creating the most recent checkpoint and thus, quickly detect delays in check point creation or writing to disk.

Measurement	Description	Measurement Unit	Interpretation
Initiated_transactions	Indicates the rate at which transactions are initiated.	Transactions/Sec
Commited_transactions	Indicates the rate at which transactions are committed.	Transactions/Sec
Rolledback_transactions	Indicates the rate at which transactions are rolledback.	Transactions/Sec	Ideally, the value of this measure should be very low.
Rollback_rate	Indicates the percentage of initiated transactions that are rolled back.	Percent	A value close to 100% is a serious cause for concern, as it implies that almost all transactions have been rolledback. Rollbacks consume processing overheads excessively and reduce database performance.
Recent_checkpoint_time	Indicates the amount of time taken to create the most recent checkpoint.	Seconds	An increase in this value under steady write load may indicate saturation on the I/O subsystem.