The asynchronous prefetch limit specifies the percentage of the pool that can be used to hold pages that have been brought into the cache by asynchronous prefetch, but have not yet been used by any queries.
Use the global async prefetch limit parameter to set the default value for the server. Pool limits, which are set with sp_poolconfig, override the default limit for a single pool.
sp_poolconfig pubs_cache, "2K", "local async prefetch limit=20"
Changes to the prefetch limit for a pool take effect immediately and do not require a restart of SAP ASE. See Performance and Tuning Series: Basics > Tuning Asynchronous Prefetch.