What is the maximum database size for a Lotus Notes® database?
The maximum database size limit for all platforms is 64 gigabyte (GB). However, depending on the file system being used, the file system might limit the size of files to a smaller size than 64 GB.
Note that very large databases increase the risks of failure and recovery time, in cases of outage. Hence, it is advised to avoid designing ever growing database, unless there is an archiving scheme (dividing data on a criterion).
From the Release 6.x Administration Guide:
Upgrading database format
After you install Lotus Domino 6 on a server, you can upgrade the format of databases on that server. The database format determines which features are available in a database. Some Domino 6 features, such as LZ1 compression and view logging, require the Domino 6 database format.
When you compact a database, the database format is upgraded.
Lotus has tested and certified databases up to 64 GB.