| OCR Text |
Show is an attractive characteristic of HELP. One reason is that there are only two HELP database-access primitives to be modified in conjunction with the development of the virtual database. Another reason is that new applications of the HELP System will continue to be built upon these database-access primitives. Modification of the virtual database system will not be required in order to support the collection of new types of data. The HELP database-access primitives use Enscribe file-access procedures. Enscribe is a product of Tandem Computers, Inc. The two data files of the HELP System are Enscribe key-sequenced files. Key-sequenced files are record oriented. Each record must have a unique primary key. 3.2 A Virtual Database for HELP 3.2.1 Overview The virtual database is a specific set of ID and DATA files on the clinical computer system. A process that opens these files is able to access any of the data in the archival database if HELP database-access primitives are used. The use of lower-level (Enscribe) file-access primitives will circumvent the virtual database management routines and therefore only provide access to records that are physically located in the virtual files of the virtual database. The modification of the Enscribe file-access primitives would have allowed a more general solution; however, it would not be practical to modify these routines. First, the general solution would be much more complex to implement because the general solution would have to support virtual read and write access for all of the 23 |
