Reversion - steps to be considered

All enterprise applications should have reversion process before deploying them into production. This is followed by most of the online applications; to take care of addressing unavoidable issues (revert back to old release, if there is no workaround). Configuration changes are key in this process. Important things to take care,

* Don't depend on back up configuration files: Always change the parameters in current configuration files. This is because even though we take back up of configuration file before deploying current release, there is a possibility that it will be changed in production environment for some other components/reasons. When we revert the release, the changes done after the release will be gone if we use back up file.

* Don't overlook any configuration changes: Do not leave any configuration change assuming that it will not affect old release. If we overlook one parameter and that can even bring down entire environment. We had such a situation while testing in Dev, one parameter has been changed from milliseconds to minutes (frequency between run). So as part of release we changed from 60000 to 1. Everything went well. We have done reversion and missed this parameter, old application assumes this as 1 and runs. Because it is 1 millisecond and it went into loop. Ultimately it brought down entire database, oops. So learned from mistake