What is it? Why is it important?

Database lock is the action taken to ensure that no further changes to study data are possible.

Two main database locks exist:

  • Interim lock performed during study conduct due to:
    • Study safety and/or efficacy concerns
    • Additional data cleaning requirements

Database locks and evaluations during study conduct must always be based on specifications and rationales given in the study protocol (e.g. safety / DSMB, efficacy concerns).

  • Final lock performed after:
    • All study data (variables) has been collected and entered in the database (eCRF)
    • Data cleaning with the aim to resolve missing or incorrect data is complete
    • All pending data queries are resolved (e.g. correspondence between monitor and study staff regarding data inconsistencies)


Interim database locks (before all data has been collected) can be planned in order to evaluate whether to continue, adapt or terminate a study. This can be due to:

  • Safety concerns (e.g. a potential high frequency of adverse events during study treatment)
  • Efficacy concerns (e.g. treatment effect compared to placebo is highly superior or has no added benefit)

Note, data analysis not based on specifications in the study protocol carries the risk of corrupting the study, as the researcher is no longer an independent bystander of the study but become biased as to study outcome.

Database locks can also be planned during long term studies, with the aim to minimise data cleaning workload once the study is terminated.


What do I need to do?

Write an SOP that describes:

  • Grounds for database lock (e.g. based on study protocol specifications)
  • Frequency and timing of lock(s) (e.g. after inclusion of 3 participants, 1st participant has completed the intended study treatment)
  • SP-INV and Site-INV responsibilities (e.g. eCRF sign-off confirming that study data is complete, correct and validated)
  • Access management (e.g. staff logins are removed to prevent further changes to the database)
  • How to document the lock (e.g. time and date of lock including implemented version of the locked database)
  • Type of statistical analysis required including any implication with respect to deviations (e.g. the study may have to be adapted or discontinued due to safety or efficacy concerns)

For more information refer to Monitoring in this Trial Guide.


Upon locking the database, it is important to document the exact date and version of the locked database. This confirms that:

  • The current and correct study database version was used by the statistician during data analysis
  • Data analysis was done after the database was locked

To ensure data quality and facilitate database lock, plan ahead and ensure that:

  • Data entries are performed on an ongoing basis, while data is still “fresh”. Hindsight backlog of large volumes of data carries increased risks of data errors and data quality concerns
  • SP-INV and Site-INVs sign-off CRFs on an ongoing basis. A task that should not be postponed to the very end. By signing-off the CRF, it is confirmed that all required data (variables) has been entered in the CRF and has been monitored to be correct
  • External data providers (e.g. laboratories) are informed of upcoming database locks to ensure that all available data (variables) is collected and integrated into the study database
  • Data monitoring visits are planned in good time before any planned database locks

Where can I get help?

Your local CTU can support you with experienced staff regarding this topic


ICH GCP E6(R2) – see in particular guidelines

  • 5.5. Trial Management, data handling, and record-keeping
  • CRF – Case Report Form
  • CTU – Clinical Trials Unit
  • DSMB – Data Safety Monitoring Board
  • eCRF – electronic Case Report Form
  • Site-INV – Site-Investigator
  • SOP – Standard Operating
  • SP-INV – Sponsor-Investigator
Development ↦ Data Handling ↦ Database Lock ↦ Procedures

Provides some background knowledge and basic definitions

Basic Protocol
Basic Statistics
Basic Monitoring
Basic Drug or Device
Basic Biobanking

Starts with a study idea

Ends after having assessed and evaluated study feasibility

Concept Protocol
Concept Statistics
Concept Drug or Device
Concept Biobanking

Starts with confidence that the study is feasible

Ends after having received ethics and regulatory approval

Development Protocol
Development Statistics
Development Drug or Device
Development Biobanking

Starts with ethics and regulatory approval

Ends after successful study initiation

Set-Up Protocol
Set-Up Ethics and Laws
Set-Up Statistics
Set-Up Quality and Risk
Set-Up Drug or Device
Set-Up Biobanking

Starts with participant recruitment

Ends after the last participant has completed the last study visit

Conduct Protocol
Conduct Statistics
Conduct Drug or Device
Conduct Biobanking

Starts with last study visit completed

Ends after study publication and archiving

Completion Protocol
Completion Statistics
Completion Drug or Device
Completion Biobanking
Current Path (click to copy): Development ↦ Data Handling ↦ Database Lock ↦ Procedures

Please note: the Easy-GCS tool is currently under construction.