Uploading Contacts: Replace Option in Everbridge Suite.
When uploading contacts from a CSV file (Contacts > Uploads > Upload to portal), there are four options; Update, Replace, Restore and Delete. This Knowledge Base Article explains the contact upload Replace option. With Update, records are updated and new records are added. With Delete, records are deleted. Replace does both. That is, new records are added, existing records are updated and unwanted records are removed. This is a great option for accomplishing all three tasks with one upload but careful configuration needs to happen or data can be lost.
The uploading contacts Replace option basically replaces contacts in entire batches called Record Types. The system will look at what Record Types are included in the upload, and then replace all of each Record Type with what is in the upload file (potentially deleting contacts).
For example, if an upload included Employee and Contractor Record Types but did not include Resident, the Replace upload option would replace ALL Employee and Contractor contacts with those in the upload file, but it would leave Resident contacts alone.
*** IMPORTANT ***
Manually added contacts can be potentially deleted using the Replace option. To protect this from happening, it is recommended that manually added contacts be given a Record Type of their own. For example, create a Record Type called Manual or something like that. Any contacts with Manual as their record type should be safe from the daily uploads, as long as those uploads do not include ANY Manual contacts themselves - the system will see there are no Manual contacts in the upload, and will skip altering that Record Type.