Free memory from another Pool location

Hello guy, im just beginner. I'm building a moduel that inserted into NGX_HTTP_ACCESS_PHASE. I have some data that i want to save and to use for along time, then i store them in a variable in location config(I knew that the best way is use shared memory to store data permanently, but i just wana try this first). Then my permanent data were stored in a pool, the pool about configuration, i can allocate memory in this pool from NGX_HTTP_ACCESS_PHASE but in this phase i canst free the data that i have just allocated. Is that true? or is something wrongs in my program ?
I'm not a english man so forgive me about my mistake, Thank you!