Growing the RWStore involves three elements: the raw file storage, the number of FixedAllocators to manage the storage and the size of the metaBits to manage the FixedAllocator storage.
The initial store size is set by the com.bigdata.journal.AbstractJournal.initialExtent property and defaults to 10 megabytes.
As more storage is required the file extent will increase by a minimum of 10% of the existing size.
As the number of allocations increases so more FixedAllocators will be required to manage them.
And as the number of FixedAllocators increases so new metaBits regions will be required and the metaBits storage increased.