Abstract: A virtual lookaside facility maintains named data objects in class-related data spaces by virtual storage, for use by user programs. Concurrently executing service processes use local copies of an access token to access the data in the data spaces. Deletion of one of the data spaces invalidates the access token so that active processes will encounter a program check on access after data deletion. An error recovery means, recognizing the invalid token as cause of the program check, provides an appropriate return code to the invoker of the service process.

Abstract: A virtual lookaside faclity is provided for maintaining named data objects in class-related data spaces in virtual storage, readily retrievable by user programs. A search order is associated with each user, specifying an ordered list of "major names" which are, in effect, sequentially searched for a specified "minor name", or data object, to obtain a virtual storage copy of that data object. As data objects are placed into a virtual cache, existence information, implicit in the naming structure, is captured and saved. This information is relied on later in retrieving objects from the cache. The data isolation provided by maintaining class data and control blocks in individual data spaces is exploited to prevent failures relating to one class of objects from affecting the others, and to handle latent program users, following failures, effectively.An LRU-like trimming technique is used to remove less useful objects from the cache when cache space is fully utilized.