Storing MemoryContext Pointers

Hi,

When I allocate a new memory context via

oldmcxt = AllocSetContextCreate(TopMemoryContext, ...)
persistent_mcxt = CurrentMemoryContext;

How can I store the persistent_mcxt in a persistent place that I'll be
able to reach it in my next getting invoked? Is that possible? If not,
how can I reach my previously created persistent data in my next
invocation?

Regards.