I have a custom import module to create soon. Part of the import is use Product_Add.

The first question to clarify, If the product is already in the catalog, that product is ignored? I think that's right, but not sure.

Following that up with the Provide log files. There is a log file and the inline files, PRV_inline.log and PRV_inline.xml. Is it correct that PRV_inline.xml is overwritten after every execution of a Provide XML file, either using the Feature function or in the Data Management import module for Importing Data in Provisioning Format?

The other question is a log question. How quickly will this grow in size? Example: I can see an XML with 100 products. If 100 already exist, will there be 100 entries that say "product already exists?"
Assuming the worst, does the log file need to be checked for file size and removed/renamed manually?