GLOSSARY alternate collating sequence - A sorting sequence other than the standard ASCII sequence that specifies the order in which Btrieve sorts keys. application - A program or set of programs, such as a spreadsheet or a payroll application, that performs a task or a group of related tasks. Also, a program written by or for a user to apply to the user's work. application interface - A program that allows access to Btrieve files from an application program. ascending - A key attribute that instructs Btrieve to collate an index in ascending order. ASCII - An acronym for American Standard Code for Information Interchange. ASCII is a 7-bit information code that defines 128 standard characters, including control characters, letters, numbers, and symbols. Btrieve - A key-indexed record manager for file handling. A function call from a standard programming language or from NetWare SQL invokes Btrieve. Btrieve Requester - The Btrieve Requester program for the applicable DOS, OS/2, Windows, or UnixWare environment that resides at a workstation and provides communication between Btrieve and a workstation application making Btrieve calls. buffer - A storage area in memory that is used to store data temporarily. cache - The area of memory in which Btrieve stores images of physical disk pages. Btrieve uses the cache to reduce the number of physical disk I/O requests. case insensitive - A key characteristic that instructs Btrieve to sort an index so that values in uppercase letters are sorted in the same order as values in lowercase letters. (For example, SANDY is equal to sandy.) chunk - Any arbitrary portion of a record, specified by its offset and length. Btrieve v6.1 allows applications to update and retrieve portions of very large records, called chunks, rather than the entire record. command file - A user-defined file that contains a sequence of commands. concurrency controls - The methods Btrieve uses to resolve possible conflicts when two applications attempt to access the same data. Controls include passive control, record locking, and transaction control. configuration - The customization of a program such as Btrieve. You can customize Btrieve through the Setup utility. configuration options - Specifications defined for Btrieve when it is loaded. Configuration options control the way in which Btrieve operates. You can use the Setup utility to change the configuration options. connection number - The unique identifier number that NetWare assigns when a workstation attaches to a server. continuous operation - A Btrieve feature that allows you to back up data files while they are open and in use. Btrieve opens the files in read-only mode to allow backup utilities to access the filesŐ static images. Btrieve stores changes to the original files in temporary files called delta files. When the backup is complete, Btrieve automatically updates the original files with the changes stored in the delta files. Btrieve deletes each temporary file as soon as all applications close the Btrieve data file corresponding to that delta file. database - A set of one or more records or files that contain information on a related subject. default - A preset option or value. For example, the default directory or disk drive is the one in which you are currently working. description file - An ASCII file containing information that the Maintenance utility commands CREATE, INDEX, and SINDEX need to perform their operations. directory - A disk structure that contains files. A directory may also contain subdirectories. DOSThe DR DOS, MS-DOS, or PC-DOS operating system. duplicatable - A key attribute specifying that multiple records in a file can have the same value in the key field. dynamic link library (DLL) - A program library that contains related modules of compiled code. At runtime, the application reads the functions in the DLL. This process is called dynamic linking. dynamic link routine - In OS/2 and Windows v3.x, a program that the operating system loads on demand (dynamically) and terminates automatically. field - The smallest meaningful unit of data in a file. file - A collection of records stored on a disk. A file is sometimes also referred to as a physical file. index - A key or a group of keys that Btrieve uses to sort a file. See also key. index balancing - The process of searching for available space in sibling index pages when a given index page becomes full, and then rotating values from the full page into the pages that have space available. Index balancing is a new feature you can activate in Btrieve v6.1 (as explained in Chapter 3, "Installing and Configuring Btrieve"). integrity control - A method of ensuring that data in a file is complete and accurate. Btrieve uses concurrency controls and shadow paging to guarantee data file integrity. See also concurrency controls and shadow paging. key - A field in a Btrieve file by which the file can be sorted. See also index. manual key - A modified form of the null key, useful in excluding particular records from the index. In a manual key, if every byte of one segment contains the null value, Btrieve excludes the key from the index. (The Btrieve Programmer's Manual refers to manual keys as "any-segment null keys.") modifiable - A key attribute that allows you to modify the key field during an update to a file. If a key is not modifiable, you cannot change the value in the key field. NetWare Loadable Module (NLM) - A server program built into server memory with NetWare. You can load or unload an NLM while the server is running. The NLM becomes part of the operating system and can access NetWare directly. NetWare SQL - Novell's relational data access system, which resides at the server as an NLM. null key A key field that can be a user-defined character. For null keys, Btrieve does not include the record in the index if the record's key value matches the null value. (The Btrieve ProgrammerŐs Manual refers to null keys as "all-segment null keys.") owner name - A password that protects data files from unauthorized access by Btrieve applications. You can assign an owner name using the Maintenance utility or by implementing a Set Owner record operation. page - A unit of a data file. A page is the smallest unit of storage that Btrieve moves between main memory and disk. Pages contain a multiple of 512 bytes (up to 4,096 bytes). pathname - The server name, volume, directory path, and filename that uniquely identify a file. pre-imaging - Storing the image of a file page before updating a record on the page. Btrieve v5.x and earlier use pre-imaging to provide recovery capabilities in case a file is damaged or a system failure occurs during an update to the file. record locking - A type of concurrency control that enables an application to lock the record it is accessing within a file. Other users can read the record, but no other user can lock, update, or delete the record until the application that holds the lock releases it. Record Manager - The server-based Btrieve Record Manager is a program that resides at the server and handles data I/O with the file system. The client-based Btrieve Record Manager resides at the workstation and handles data I/O with the file system through operating system calls. referential integrity (RI) - The assurance that when a field in one table references a field in another table, changes to these fields are synchronized. Requester - A program that resides at a workstation and passes requests from an application to a server-based application. roll back - Aborting a transaction and undoing all the changes made to a file during the transaction, thus restoring the file to the state it was in before the transaction began. See also transaction. roll forward - Recovering changes made to a Btrieve file between the time logging is initiated and a system failure. See also roll back and roll in. roll in - Writing to a Btrieve original file all the changes made to the corresponding temporary file during the continuous operation backup period. When the backup is complete, Btrieve automatically updates the original file with the changes and deletes the temporary file. See also continuous operation. segmentedA key attribute that allows a key to consist of one or more fields (or segments). Sequenced Packet Exchange (SPX) - A Novell communication protocol that monitors network transmission to ensure successful delivery. SPX runs on top of Novell's Internetwork Packet Exchange (IPX). shadow paging - A technique that Btrieve v6.x uses to ensure data integrity. When a user needs to change a page, Btrieve makes the change to a physical shadow page, which is a virtual copy of the original page. When the change is committed, Btrieve designates the shadow page as the current page, and the original page becomes available for reuse. sign trailing separate (STS) - A COBOL data type that is basically a numeric data type, represented as an ASCII string. STS is right justified and padded with leading zeros, and it has the sign byte at the end. supervisor - The person responsible for the administration and maintenance of a network, a database, or both. A supervisor has access rights to all volumes, directories, and files. thread - A separate stream of execution within a program. transaction - A set of related operations that constitutes a logical unit of work. The application performing the transaction requires that either all or none of these operations be performed. user - Someone who is authorized to log in to a network and/or database when security is installed and who has access rights to specific filenames, directories, and files. Variable-Tail Allocation Table (VAT) - An array of pointers to the variable-length portion of Btrieve records. The VAT is implemented as a linked list.