There are no fixed size limits for things like forms database files in an Avalanche configuration as each test and environment have too many variables to account for which all use resources at different rates.
If you are looking to use a large number of forms files (10+) and/or formsDB file(s) with large line counts (~25-100k) the recommended approach is to start small and scale up, for example if you need a formsDB file of 50k lines, try 10k first, then 20k and so on. You will know a test limit has been reached when the test fails to start with larger files but works with smaller files.
It's important to have specific testing goals and limits in mind before creating a test case which will allow you to approach it in the best possible way with maximum resources available.
If you continue to have questions or concerns please open a server request (SR) with global services via email@example.com, online http://support.spirent.com or via phone: 1-800-SPIRENT