Maximize or force full garbage collection in Xodus database

Question

We have an application that writes lots of data in a Xodus database. It actually writes so much data that the garbage collector cannot keep up with freeing old files.

My question therefor is, are there any recommended settings for "maximum GC", or is there a way to force Xodus to "stop" (disallow writes) and do a full garbage collection at some point during the night?

Edit (requested information)

Non-default settings:

• GcFilesDeletionDelay = 0
• GcMinUtilization = 75
• GcRunEvery = 1 (for testing)
• GcRunPeriod = 1 (for testing)
• GcTransactionAcquireTimeout = 1000
• GcTransactionTimeout up to 120000 (for testing)
• Fiddling with these settings has not increased GC throughput in a relevant way

What we do:

• We have a single import thread that writes exclusively to an environment store. Data is written permanently throughout the day.
• There are many parallel threads that read the data using read only transactions.
• The data basically is measurement data in the form (location, values...)
• 50% of values get updated every day
• There are roughly 8 million records in the database, the database currently has 122 GB on disk with 75% free space (as printed by the GC)
• The VM has 20 GB of RAM, the environment store may use up to 25%