Fallback is the process of shifting the operations back to the previous active data center after resolving all the issues due to which the data center had failed.

For example, consider two data centers configured, Data Center-1, Data Center-2, where Data Center-1 is active and operational and Data Center-2 is standby. Due to an outage failover, planned or unplanned failover occurs from Data Center-1 to Data Center-2. POM services resume on Data Center-2 and Data Center-2 becomes fully operational. After the issues with Data Center-1 are resolved and the user has to move all operations from Data Center-2 back to Data Center-1. Therefore making Data Center-1 operational again and making Data Center-2 standby as before. This reverting to previously operational Data Center-1 is called fallback. Therefore a fallback is done on a data center that was previously active or which had failed earlier.

As operations are being shifted from one data center to another, Fallback is similar to Failover. Based on whether the Fallback is planned or abrupt, it is categorized as planned-Fallback or unplanned-Fallback.