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OPL DATA FILE AND DATABASE HANDLING

Data granularity: The data within a P2P system can be accessible at many degrees of granularity. At the atomic granularity level, data consists of a collection of indivisible objects, e.g., complete MP3 files. For data placement at this level, we have to either place an entire object at a peer, or not at all; this is the semantics currently supported by today’s P2P systems. At the hierarchical granularity level, sets of objects can be grouped into larger objects, thus forming hierarchies. For example, multiple MP3 files may be grouped into an album, and albums into collections; for the data placement problem at this level, we. | OPL DATA FILE AND DATABASE HANDLING Copyright Psion Computers PLC 1997 This manual is the copyrighted work of Psion Computers PLC London England. The information in this document is subject to change without notice. Psion and the Psion logo are registered trademarks. Psion Series 5 Psion Series 3c Psion Series 3a Psion Series 3 and Psion Siena are trademarks of Psion Computers PLC. EPOC32 and the EPOC32 logo are registered trademarks of Psion Software PLC. Copyright Psion Software PLC 1997 All trademarks are acknowledged. OPL CONTENTS DATA FILE HANDLING.1 FILES RECORDS AND FIELDS.2 CREATING A DATA FILE.2 LOGICAL NAMES.2 FIELDS.2 OPENING A FILE.3 SAVING RECORDS.4 THE NUMBER OF RECORDS.5 HOW THE VALUES ARE SAVED.5 MOVING FROM RECORD TO RECORD.6 DELETING A RECORD .6 FINDING A RECORD.6 WILDCARDS.6 MORE CONTROLLED FINDING.7 CHANGING CLOSING THE CURRENT FILE.8 EXAMPLE - COPIES SELECTED RECORDS FROM ONE FILE TO ANOTHER.8 CLOSING A DATA FILE. 8 KEEPING DATA FILES COMPRESSED. 9 SERIES 3C AND SIENA DATA FILES AND THE DATA APPLICATION.9 SERIES 5 DATABASE HANDLING .11 THE SERIES 5 DATABASE MODEL.1 2 DATABASES TABLES VIEWS FIELDS AND FIELD HANDLES . 12 CREATING DATABASES AND TABLES.12 LOGICAL NAMES. 12 FIELDS.13 OPENING DATABASES AND TABLES.1 3 TRANSACTIONS.13 RECORD POSITION .14 SAVING RECORDS.1 4 THE NUMBER OF RECORDS. 14 CLOSING VIEWS AND DATABASES.14 INDEXES.14 COMPACTION.1 5 OPENING A DATABASE CREATED BY THE DATA APPLICATION.1 5 INDEX . 1 6 DATABASE INFORMATION OPL DATA FILE HANDLING You can use OPL to create data files databases like those used by the Data application. You can store any kind of information in a data file and retrieve it for display editing or calculations. This section covers Creating data files Adding and editing records Searching records Using a data file both in OPL and in the Data application The Series 5 and the Series 3c database models differ quite substantially. However the Series 3c method of database programming except for some removed keywords