I want to delete few contact in SFMC. I know how to delete contacts but just want to know if other related data like email open rates, email sends reports will remain in the system or not.
The information will remain in the system - but in unrecognizable format.
Contact deletion does also not remove the Contact (any any related information) from your custom non-sendable Data Extensions, Send Logs and FTP files.
Tracking data for deleted subscribers and contacts are retained in anonymized format and cannot be linked to a specific record. Tracking and reports show clicks from firstname.lastname@example.org and an IP address of 0.0.0.0 for deleted records.
There are two methods of deleting contacts:
1) Contact Deletion via Contact Builder
This is a full hard delete and will NOT retain individual tracking data such as opens, clicks etc. However it will keep the aggregate stats (overall open rates, CTR, etc.) but not the individuals that opened and clicked. This method of deletion completely purges the contact from all sendable DEs, Journeys, automations, send tracking, and Data Views. This method is recommended for purging data to meet GDPR requirements or to reduce your overall number of contacts to avoid additional costs associated with going over your contact limit. See https://help.salesforce.com/articleView?id=mc_cab_contact_deletion.htm&type=5
2) Deleting Subscribers in AllSubs
This is more of a soft delete. Individual tracking data is retained in anonymised format.