Data processing: database and file management or data structures – Database design – Data structure types
Reexamination Certificate
1999-01-15
2001-12-11
Mizrahi, Diane D. (Department: 2171)
Data processing: database and file management or data structures
Database design
Data structure types
C707S793000, C707S793000
Reexamination Certificate
active
06330571
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the data processing field, and more particularly, relates to a method and computer program product for implementing datalink path protection.
DESCRIPTION OF THE RELATED ART
The DATALINK data type is one of the basic building blocks for extending the types of data that can be stored in database files. The idea of a DATALINK is that the actual data stored in the column is only a pointer to the object. This object can be anything, an image file, a voice recording, a text file, and the like. The method used for resolving to the object is to store a Uniform Resource Locator (URL). This means that a row in a table can be used to contain information about the object in traditional data types, and the object itself can be referenced using the DATALINK data type. The user can use new SQL scalar functions to get back the path to the object and the size of the object. With the DATALINK data type, there is a fairly loose relationship between the row and the object. For instance, deleting a row will sever the relationship to the object referenced by the DATALINK, but the object itself might not be deleted.
Datalink support allows users to designate directories in a root file system to contain datalink objects. The datalink designations provide referential integrity of the linked files that are stored in the native file system. Once a directory is marked as a datalink designation, access to all objects in that directory subtree is through the datalink file manager (DLFM). When the objects in the datalink designations are marked as datalink objects, the DLFM creates a prefix table containing the path of the objects. Any attempt to access, remove, or rename these objects will be intercepted by the DLFM which prevents any deletion or renaming of the datalink objects by checking the paths against the stored prefix list.
Datalink support prevents a rename or removal of a datalink object. This is done by checking the path of the object being renamed or removed against a list of prefixes maintained by the datalink file manager. For example, if /a/b/c is a datalink designation and /a/b/c/d is a file marked as a datalink object. Deletion or rename of /a/b/c/d will be prevented by the datalink file manager. However, the path leading to the datalink object sometimes may be renamed if the directory object prior to the datalink designation gets renamed. For example if /a/b/c is a datalink designation, /a/b can be renamed. This would cause inconsistencies in the datalink's prefixes.
This problem is not addressed by any other platforms providing datalink support mainly because this has a significant performance impacts.
SUMMARY OF THE INVENTION
A principal object of the present invention is to provide a method and computer program product for implementing datalink path protection. Other important objects of the present invention are to provide such method and apparatus for implementing datalink path protection substantially without negative effects and that overcome many disadvantages of prior art arrangements.
In brief, a method and computer program product are provided for implementing datalink path protection. A datalink designation is created in the computer system and a datalink indicator is turned on. A corresponding datalink path for the datalink designation is stored in a predefined prefix table.
In accordance with features of the invention, the datalink indicator is used for processing a directory rename or remove operation.
REFERENCES:
patent: 5678042 (1997-10-01), Pisello et al.
patent: 5987506 (1999-11-01), Carter et al.
patent: 6108285 (2000-08-01), Freeman et al.
(IEEE publication) TCP/IP performance with random loss and bidirectional congestion by Lakshman et al. in Networking IEEE/ACM Transactions, pp. 541-555 vol. 8 No. 5 (10-2000).*
(IEEE publication) Designn issues for high-performance active routers by Wolf et al. in Selected areas in communication, vol. 19; No. 3, pp. 404-409 (Mar. 2001).
Bills Raymond
Kumar Atul
International Business Machines - Corporation
Mizrahi Diane D.
Pennington Joan
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