File management overview
File management tasks
You might want to designate one or more persons at your site to be responsible for all tasks related to file management.
File management tasks include:
- Creating, maintaining, and administering Model 204 database files
- Organizing Model 204 database files for maximum efficiency in data retrieval
The users performing file management tasks (thus acting in the role of "file manager") must be proficient in:
- Data allocation, storage, and retrieval, and transaction backout (as required for all database management systems)
- Tasks unique to Model 204 (as described in the file management topics)
A good file manager should understand application design and SOUL coding techniques to assist the application developers in their tasks.
The file manager works closely with the system manager. System manager duties include starting, stopping, and monitoring the Model 204 system and setting user priorities and security.
File manager privileges
File manager privileges are established at the file level: privileges for each file are defined on the password used to open the file or the PRIVDEF (default) file privileges when no password is supplied on the file open.
Dictionary/204 File Management Subsystem facility
If you use the Model 204 data administration product, Dictionary/204, you have access to the File Management Subsystem facility (FILEMGMT). You can choose to create and maintain Model 204 files using FILEMGMT instead of entering commands in a file or on the command line.
FILEMGMT is a full-screen interface that prompts you for the specific file definition information it needs to automatically construct the Model 204 commands that create and define the file. FILEMGMT provides automatic file sizing and other time-saving features.
FILEMGMT also stores the entries in your site's Dictionary for the files, fields, records, and field groups that you create. For more information on the Dictionary, refer to Dictionary/204 overview.
In addition to creating new files and providing automatic file sizing, you can use FILEMGMT to add fields or records to existing files, to change file parameters or file size, and to view or copy file information. FILEMGMT tasks are described throughout the file management topics.
Even if you intend on using the FILEMGMT APSY, you should have a solid knowledge of the rules and techniques involved in the creation and maintenance of Model 204 files.
You can perform most file management tasks in two ways:
- Manually creating procedures containing commands or directly on the command line
- Using the File Management Subsystem Facility (FILEMGMT)
There are file management topics to describe each way of performing a task.
The following tables describe where to find information about file creation and file management tasks. Where applicable, the Order column indicates the order in which you should perform the tasks.
|Order||Task||For information, see ...|
|1||Understanding Model 204 file architecture and file managment||File architecture overview
File management overview (this page)
|2||Designing your files for most efficient storage and best performance; determining size and security requirements||File design|
|3||Designing your Model 204 data structures for effective and efficient processing||Record design
Field group design
(if you create the file manually)
|Calculating file size:
Note: These calculations are done for you if you create files using FILEMGMT, which is the recommended method. But the information is useful to know in any case.
|File sizing introduction|
||Creating a file|
|6||Initializing files||Initializing files|
|Task||For information, see ...|
|Loading data into a file
Loading raw data from a sequential data set into records in a Model 204 file
|File loading techniques|
|Managing deferred updates||Deferred update feature|
|Managing the size of file tables; options and parameters for automatic or manual increases||Resizing tables|
|Safeguarding file integrity and recovering files; backing out transactions; running media recovery||File integrity and recovery
Transaction back out
|Dumping and restoring files: creating a backup copy of your data; moving files; adjusting internal space calculation||File dumping and restoring|
|Managing Model 204 security for logins, files, and records; defining passwords and file privileges||Model 204 security features|
|Monitoring file use on the system and system performance; compiling file statistics||File statistics and tuning|
|Reorganizing files||File reorganization|
|Displaying a field, file, or record; broadcasting a file message||Field display and message broadcast|