FILEMGMT overview: Difference between revisions

Revision as of 23:58, 16 May 2017

Prerequisites

In order to use FILEMGMT:

You must have Dictionary/204 and its subsystems running.
You should have an understanding of Model 204 file management. See File management overview for details.
You need file management privileges and the appropriate Model 204 privileges:
- Creating a new Model 204 file requires login account privileges that include superuser privileges.
- Changing an existing file requires a Model 204 password indicating that you have the necessary update privileges for the file.

Overview

The Dictionary/204 File Management Subsystem facility, FILEMGMT, is a full-screen interface to Model 204 file management. The facility enables you to create Model 204 files quickly, reliably, and securely. You define a file and its contents on the series of screens that FILEMGMT provides. FILEMGMT uses your definitions to:

Construct the Model 204 commands that create the physical file
Store the appropriate entries in your installation's dictionary

By combining the two operations, FILEMGMT eliminates the need to enter this information twice. FILEMGMT validates the information for accuracy and consistency, and it creates and stores all necessary dictionary entries and references.

FILEMGMT does more than create new files. You can use the facility to:

View existing file data
Reset file parameters
Add fields, records, and field groups to existing files
Calculate and change the size of a file
Copy files, fields, and records

FILEMGMT maintenance functions

FILEMGMT consists of the following maintenance functions:

File maintenance
Field maintenance
Record maintenance
Field group maintenance

These maintenance functions let you define FILE, FIELD, RECORD, and FIELD GROUP entries, as well as modify and delete these entries. The facility also creates the actual files, fields, records, and field groups that correspond to the dictionary entries that you have defined or modified.

Each maintenance function has its own full-screen interface that you can select from the FILEMGMT primary screen. Using the facility screens you can specify the characteristics and relationships of your files, fields, records, and field groups. The FILEMGMT facility also sizes files automatically based on information you provide about file characteristics. The section File sizing overview explains in more detail how file sizing works.

FILEMGMT and command execution

After you have defined the characteristics and relationships of an entry, FILEMGMT stages your entry for the specified commands. The commands can be executed in one of four active or inactive modes, depending upon the execution options that are supported at your installation. Your dictionary administrator selects a default mode, but you can override that selection with another supported option. The section Dictionary/204 and staging explains the execution options in detail.

When the commands are executed, FILEMGMT creates the file, field, record, or field group as you have defined it. The facility also creates the corresponding (non-staged) dictionary entry. The section Staging entries explains staged and non-staged entries.

If it becomes necessary to modify an existing file, FILEMGMT locks all the file, field, record, and field group definitions for that file to protect the integrity of the dictionary data. The section File locking explains file locking.

Staging entries

FILEMGMT coordinates these general activities:

Construction and execution of Model 204 commands
Storage of entries in your installation's dictionary

The activities can be completed in a single FILEMGMT session or can be performed across multiple sessions. A dictionary entry containing your specifications is staged until all commands pertaining to the entry are executed. The entry is described as existing once execution is completed.

Some FILEMGMT functions let you operate on staged entries; others do not. The following descriptions of the FILEMGMT screens specify the circumstances under which you can redefine, delete, and rename staged entries.

Dictionary/204 and staging

Internally, Dictionary/204 manages staging by supporting two copies of every dictionary entry affected by your request. For example, if you are performing a file recreate, your request might affect entries of the following entity types in your installation's dictionary:

FILE FIELD RECORD FIELD GROUP

Copies of these entries exist until your commands have been executed. The copies have the entity types of:

STAGED FILE STAGED FIELD STAGED RECORD STAGED FIELD GROUP

The two copies are identical except that the staged version contains:

COMMAND attribute	Specifies the command to be generated
COMMAND STATE attribute	Indicates the status of the command

A file create request, unlike a file recreate, has only staged entries.

FILEMGMT copies an existing (or non-staged) entry to a staged entry when you initiate a change to a file, field, record, or field group. When all relevant commands have been executed, FILEMGMT copies the staged entry to a non-staged entry by deleting the non-staged entry and renaming the staged entry as non-staged.

How commands are executed

FILEMGMT constructs Model 204 commands from the information you enter. The commands, when executed, perform the functions you requested from the primary screen.

The execution of a command depends upon the following factors:

Completeness of the request for a FILEMGMT function
For example, a file create function is not complete when you finish entering a file description, because the file must be sized. FILEMGMT must complete the description to construct the Model 204 commands that perform the create operation.

Until your request is completely specified, and until the commands constructed from the request have actually been executed, your request is considered to be staged.

To execute the commands, you advance to the Execute Commands screen, select the Model 204 commands that are waiting to be executed, and press the F6 (EXEcute) key.
Execution option you select
When Dictionary/204 is installed, the dictionary administrator determines which execution options are available to FILEMGMT users and which one is the default option. The execution option determines how staged Model 204 commands are executed on the Execute Commands screen.

The execution options are:
- Active immediate
- Active delayed
- Inactive with commands written to a procedure file
- Inactive with commands written to a directed output file

Dictionary/204 provides an option for requiring that all commands against files be executed through the FILEMGMT interface. See the "File Management options" section in the Rocket Model 204 Dictionary/204 and Data Administration Guide.

Execution options

The options provided by FILEMGMT are listed in the following table. They are more fully described again in Execute Commands screen.

Note: If you select Inactive mode, then the Dictionary/204 files are updated, but not the physical files.

Option	Commands selected on the Execute Commands screen are...
Active immediate	Executed as soon as FILEMGMT verifies that you have the necessary privileges to execute the commands.
Active delayed	Updated as pending and are executed at a later time in batch mode. FILEMGMT verifies that you have the necessary privileges to execute the commands before it flags them as pending. Consult the Rocket `Model 204` Installation Guide for your operating system for information about the JCL or CCAIN statements you need to include for a batch run.
Inactive USE file	Not executed. Instead, they are generated and written to a directed output USE file. You specify the name of this file on the Execute Commands screen. OUTFILE is the default if you do not specify a file name. A default USE file can be defined by the dictionary administrator in the Facility Administration feature of the Dictionary Administration facility or obtained from the user's ACCOUNT entry. The section Execute Commands screen describes the JCL you need to include for the USE file.
Inactive procedure file	Not executed. Instead, they are generated and written to a procedure file. You specify the name of the procedure file and its password (if any) on the Execute Commands screen. The dictionary administrator can define a default procedure file in the Facility Administration feature of the Dictionary Administration facility.

File locking

FILEMGMT provides a file locking capability to control file access and enhance data integrity. While you are creating a file or making any changes to the file definition, the file lock prevents other users from changing the file's:

Definitions
Fields, records, and field groups
Parameters and other characteristics

The file lock is maintained until you release the file by either executing or deleting the commands that FILEMGMT constructed. Your work can span multiple FILEMGMT sessions, if desired. Dictionary/204 maintains the file lock across sessions by keeping track of the account name. Only users who log in with the appropriate account name have access to the file.

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