The ACCESS Query Language (AQL) is a D3 facility used to retrieve and output data and consists of the List preprocessor, the Select processor, and the Output processor. AQL is a system-level information retrieval language that allows users to query their database without writing complex programs.
An account is a collection of logically related files. Each account has a master dictionary (MD), where the vocabulary for the account resides. This includes items such as commands, Procs, menus, macros, connectives, modifiers, file-defining items (D-pointers) and synonym-defining items (Q-pointers).
An active list is a list of strings for use in a subsequent process that handles items one at a time. Typically, a list contains item-IDs for subsequent processing, but a list can actually contain anything. For example, the statement, select entity creates a list of item-IDs, while the statement, select entity name creates a list from the contents of each entity item’s name attribute.
Each server can be given an alias to avoid having to tie a D3 object to a given computer on the network. For example: When creating an accounting database, it is better to use an alias (such as Accounting) for the server name, rather than its physical network name.
Backward link zero (BLZ) is a particular system error. A frame containing data, either workspace or file system data was not properly linked to a previous frame of data. Instead, this backward pointer was zero. The system was traversing data backward and ran off the beginning of the data.
Beginners All Purpose Symbolic Instruction Code (BASIC) is a third generation programming language originally developed at Dartmouth College in the early sixties. COBOL and the various forms of BASIC taken as a whole are the two most popular programming languages of all time.
A cursor control block is a binary item that contains the codes and control strings pertinent to the terminal in question. Each system functions (@(-(n))) has its own array position, and the system cursor function searches this item for control strings such as clear-screen, clear to end of screen, and so on.
External format describes data that has been externally converted using one of the conversion or processing codes provided with D3. As a general rule, external format means data is in a human-readable format.
Every file on the system has a special frame attached to it called a file control block or FCB. These frames contain information about the file, including index pointers and their compiled (algebraic) processing codes, the file D-pointer information for editing, pointers, and workspace used by the system when calling FlashBASIC subroutines from file dictionaries.
Attributes 5 and 6 of file-defining items can contain retrieval and update lock codes respectively. These codes are used to restrict access to certain data files and master dictionaries. Lock codes are sets of characters used as codes. Multiple lock codes are separated by value marks. The first lock code (retrieval or update) in a master dictionary or file dictionary must be matched in attribute 6 (key) of the user’s item in the users file to allow access to the file or master dictionary. If the lock code does not match, access is denied.
The file reference is the name of a file in the master dictionary to which the user is currently logged. It can also be a synonym file name. The file name can be preceded by the literal word dict to access the dictionary of the file instead of the data portion of the file. The default is data. In some cases, data may be specified to indicate only the data portion of the file.
A D3 service, normally started automatically at boot time on a Windows server that services file system requests. Each D3 file server must have an FSI service or process started to be able to access the D3 tables.
FlashBASIC is a high-level programming language that is an extension of the Dartmouth BASIC (Beginners All-purpose Symbolic Instruction Code) language. It is the principal programming language bundled with the D3 system and was designed for the implementation of application requirements not handled by standard D3 functionality.
A frame is the basic storage area of the system. Each frame is addressed by its numeric frame ID (FID), beginning with frame 1, and ending at a frame called maxfid. Maxfid is determined by the actual size of the disk and the size of data frames.
A full restore is the opposite of a full save or file-save. A full restore is the process of reloading the entire file system from either a file-save tape or from the original sys-gen media provided with your system.
Hot Backup is a configuration where one machine is in a standby mode, ready to take over the load from a failing system. Starting with D3 9.0, Hot Backup now tests to confirm that a license has been purchased.
Internal format is the data format resulting when data is internally converted using one of the conversion or processing codes provided with D3. As a general rule, internal format refers to the manner in which data is stored inside the system.
An item-ID is a unique identifier by which an item can be retrieved from a file. An item-ID may be any length up to 100 characters. It can be made up of any characters except the system delimiters; sm, am, vm, svm, or sb, and any character with an ASCII value 247 or greater. If any of these reserved values are used in an item-ID, the item-ID will be truncated at the first use of such a character. It is recommended that characters with ASCII values greater than 127 not be used since they may not display or show as different symbols on different display or printing devices.
Any command or program can be interrupted during execution by pressing the active level pushing key, (usually the BREAK or ESC key). When a command or program is interrupted, the system stops execution and saves all parameters so that execution can be resumed exactly where it was interrupted. When a process is interrupted at the normal system level, the system prompts with two colons. At this point the command or program is said to be pushed one level.
Linked or dynamic overflow are the additional frames attached to a file. As files expand and contract, additional frames are added to or removed from the groups in the primary file space. All of these extra frames are called linked or dynamic overflow and the number of frames is always changing.
The Name service allows clients to locate the service they need without knowing where and how to reach the server providing the service. To perform this service, Name service hides the network location and network protocols behind a symbolic service identification. This mechanism makes the application independent from the details, allowing, for example, for redistributing the server application from one system to another without any change in the client applications.
A phantom process is a process that is initiated at a terminal and detaches itself from that terminal for execution independent of that terminal. It is processed as a background task and the results display on the initiating terminal when the process is complete.
A Process ID (PID) uniquely identifies a UNIX process. On D3, each D3 process is a UNIX process, and, therefore, is assigned a PID by UNIX. D3 processes are usually identified by their D3 port number (from 0 to the maximum number of ports), as usual. It is sometimes necessary to identify the PID of a D3 process. The PIDs are displayed by the TCL commands list-users, pid, psr and by the UNIX command d3.
Primary file space is the initial space set aside for a file and is specified as a number of frames in the create-file command. For instance, if a file data level is set aside using 11 frames as its modulo, it has 11 frames in its primary file space.
Restricted system access means that a user has been denied access to TCL. Users can be denied access to TCL by placing the character r in the options attribute (Attribute 9: Attribute type) of their item in the users file. When this restriction is active, users are returned to the system logon program when they exit a process by pressing the BREAK key, if it is enabled.
If any process, such as a TCL command or a FlashBASIC program is executed from an account that does not have retrieval and/or update privileges for a file, and then attempts to read and/or write to that file, the process terminates with an error message indicating that the file is access protected.
A segment mark is the specific metacharacter used within D3 items. The segment mark is not actually part of data. Rather, it is used as an item delimiter, and is automatically appended to the end of an item when written to disk.
Whenever requesting a software change, please provide as much of the following information to Rocket as you can. This form can be mailed or faxed to Rocket. Software Change Requests can also be phoned into Rocket.
Also known as Q-pointers, synonym-defining items are used in account master dictionaries to point to other files. A Q-pointer is a file alias that defines a path to an existing file that resides in the system under another name, or in another account, or both. A Q-pointer can reference any file in the system, including those within the same account.
All processes that handle magnetic media are classified as tape handling commands. All references to media and tape mean the same thing. Control is returned to the calling program when the user quits from a parity error.
Through the OSFI, it is possible to access UNIX files as if they were D3 items, using AQL, BASIC, FlashBASIC, and so on. This section describes the format of the Q-pointer, the file structure and the access rules.
User exits allow direct references to assembler routines known as modes. These are generally not needed for new applications and are provided primarily for backwards compatibility and specialty utilities that must access internal structures.