EP0352447A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Virtual lookaside means and method
Assignee: International Business Machines Corp
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Filing: 1989-06-06
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Granted: —
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Expires: 2009-06-06
Abstract
Abstract A virtual lookaside facility 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 named" 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.
Inventors
- 👤 David Douglas Brown
- 👤 Wayne John Morschhauser
- 👤 Rick Francis Reinheimer
- 👤 Michael Dustin Swanson
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-27 06:23
CPC Classifications
G; G06; G06F; G06F12/00; G06F12/02; G06F12/08; G06F12/12; G06F12/121; G06F12/0802; G06F12/0866; G06F12/10; G06F12/1027; G06F12/1036; G06F12/1045; G06F9/00; G06F9/06; G06F9/44; G06F9/448; G06F9/4488; G06F2212/00; G06F2212/31; G06F2212/311
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
92 words
Virtual lookaside means in a central electronic complex comprising system resources and an operating system for managing said system resources, characterized by data objects having names comprising a class name, a major name, and a minor name; by a virtual storage cache capable of storing said data objects; by means for defining, on a user basis, a search order of major names for all minor names within a class; and by existence table means for determining whether a searched for and found data object may be used from said virtual storage cache.
Claim 2
Dependent Claim
92 words
Virtual lookaside means in a central electronic complex comprising system resources and an operating system for managing said system resources, characterized by data objects having names comprising a class name, a major name, and a minor name; by a virtual storage cache capable of storing said data objects; by means for defining, on a user basis, a search order of major names for all minor names within a class; and by existence table means for determining whether a searched for and found data object may be used from said virtual storage cache.
Claim 3
Dependent Claim
87 words
Virtual lookaside means of claim 1, characterized in that the existence table means comprises a table associated with a minor name, the table having at least one entry associated with a major name belonging to a class, the entry having a first value to indicate that the minor name does not exist among a set of minor names associated with said major name, and having a second value to indicate that the minor name may exist among said set of minor names associated with the major name.
Claim 4
Dependent Claim
52 words
Virtual lookaside means of claim 2, characterized by means for isolating data objects and control blocks associated with each of said classes so that damaged data may be purged on a CLASS basis; and by means for detecting that class data, reconstructed after a failure, is no longer accessible by latent transactions.
Claim 5
Dependent Claim
46 words
Virtual lookaside means of claim 3, characterized in that the means for isolating data objects comprises a first data space containing only control blocks associated with a single class of data objects, and a second data space containing only data objects belonging to said single class.
Claim 6
Dependent Claim
67 words
Virtual lookaside means of claim 4, characterized in that the means for detecting comprises a first data sequence number associated with said latent transactions, a second data sequence number associated with said damaged data, and a third data sequence number associated with said reconstructed data such that said first data sequence number matches said second data sequence number, but does not match said third data sequence number.
Claim 7
Dependent Claim
218 words
Virtual lookaside method characterized by identifying a search sequence for major names, said sequence indicating an order for searching for a minor name within said sequence of major names such that a search commences with a first major name in said sequence of major names, and terminates when a major name containing said minor name is identified or when all major names have been searched; by associating said search sequence with a user program; by placing in virtual storage managed by said VLF a copy of a data object having a minor name, said minor name belonging to a major name, said major name belonging to a class; by placing existence information, derived from said search sequence and from said major name to which said minor name belongs, in an existence table, when said user program so places one of said data objects in said virtual storage managed by said VLF, said existence information indicating whether said minor name is known not to exist in all of said major names occurring earlier in said search sequence; by using said existence information to determine if a requested data object may be provided from said virtual storage managed by said VLF; and by providing said copy of said requested data object to a requestor if said copy may be valid.
Claim 8
Dependent Claim
218 words
Virtual lookaside method characterized by identifying a search sequence for major names, said sequence indicating an order for searching for a minor name within said sequence of major names such that a search commences with a first major name in said sequence of major names, and terminates when a major name containing said minor name is identified or when all major names have been searched; by associating said search sequence with a user program; by placing in virtual storage managed by said VLF a copy of a data object having a minor name, said minor name belonging to a major name, said major name belonging to a class; by placing existence information, derived from said search sequence and from said major name to which said minor name belongs, in an existence table, when said user program so places one of said data objects in said virtual storage managed by said VLF, said existence information indicating whether said minor name is known not to exist in all of said major names occurring earlier in said search sequence; by using said existence information to determine if a requested data object may be provided from said virtual storage managed by said VLF; and by providing said copy of said requested data object to a requestor if said copy may be valid.
Claim 9
Dependent Claim
66 words
Method of claim 6, characterized by the step of invalidating said copy of said requested data object if said requested data object is changed after said copy is placed in said virtual storage managed by said VLF; by the step of trimming older objects from said virtual storage managed by said VLF when an available amount of said virtual storage is less than an installation limit.
Claim 10
Dependent Claim
94 words
Method of claim 6, particular for the recovery of virtual storage data, characterized by isolating a class of data from other classes of data; by deleting said isolated class of data when said class contains damaged data; by reconstructing and again isolating said damaged data; by detecting that latent transactions may no longer access said deleted data; by causing said latent transactions to fail predictably on detecting said failure to access said deleted data; and by allowing transactions which access data in said other classes, or which access said reconstructed data, to proceed normally.
Claim 11
Dependent Claim
56 words
Method of claim 8, characterized in that the isolating step comprises placing all data objects in said isolated class in a first Data Space containing no data objects belonging to any other class, and placing control blocks associated with said isolated class in a second Data Space containing no control blocks associated with any other class.
Claim 12
Dependent Claim
50 words
Method of claim 9, characterized in that the detecting step comprises comparing a first sequence number associated with said latent transactions, with a second sequence number associated with said reconstructed data, when said virtual storage data is accessed, and determining that said first and second sequence numbers do not match.
References Cited (Backward Citations)
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