Normal data processing access is through an item structure named
CRSP_ITM. CRSP_ITM includes metadata describing the item as well as the actual data retrieved from the database. The metadata is set once by
crsp_itm_open, but the data that is loaded can change each time the
crsp_itm_read function is called.
The item handling functions hide the internal storage and report the data according to
itm_name and keyset, which can be found from among the loaded items with the item look-up function,