Database lock is a significant milestone in the life cycle of a clinical trial and one of the final steps taken before submitting the information to the FDA. It should be done after a final quality check and data validation via the monitor and sponsor team but before data is extracted from the electronic data management group and formatted for submission. After last patient/subject, last visit has occurred, the data quality review and last monitoring visit can be scheduled for study site close out. Once all queries are resolved and data considered cleaned, the Principal Investigator (PI) will need to sign off that all data is complete and verified to lock at the subject casebook level. Then all access rights will be removed from the database and data cannot be changed.
For specifics on locking a database in CRMS in REDCap, the following resources may be accessed (link to REDCap and CRMS).
When you are serving as a sponsor investigator the entire database process and documentation, is your responsibility. On investigator initiated studies, you will just be singing off on your data as the PI.