metaBits define storage areas within the store for the FixedAllocators. The store header explicitly records the address of the metaBits data. The metaBits data manages a number of regions in a similar way to the FixedAllocators; a region of a set size has a start address and a number of bits for allocations. This enables the RWStore to determine the locations of the FixedAllocators.
The metaBits themselves are allocated using the standard allocators and a central part of the RWStore commit protocol ensures their pre-allocation.
The various protection mechanisms for transactions and sessions are not relevant for metaBits storage since this operates at the level of application allocations from the FixedAllocators and is supported by either "transient" data maintained in memory or "committed" data maintaining the deferred free structures.