To change the size of an existing cache, specify the cache’s name and the new size.
If you increase the size of an existing cache, all of the added space is placed in the smallest pool.
To reduce the size of an existing cache, all of the space must be available in the logical page size pool. You may need to use sp_poolconfig to move space from other pools to this pool.
If you have a database or any nonlog objects bound to a cache, you cannot change its type to logonly.