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version 2004 (Modified)
4D Open for 4th Dimension routines are called from 4th Dimension or 4D Client. The following diagram shows how 4D Client and 4th Dimension can access 4D Server databases:
4D Open for 4th Dimension enables you to establish multiple connections to a single 4D Server or to connect to multiple 4D Servers simultaneously from 4th Dimension or 4D Client.
4D Open for 4th Dimension is a set of external functions. It allows you to perform the following database operations:
Connect to a 4D Server Database
You can connect to one or more 4D Server databases simultaneously. During this stage, you initialize the client application and workstation and select the database. You can specify the database name procedurally or you can allow the user to select a database using a dialog box.
Access the Structure Definition
You can retrieve the names of the tables and fields and the definitions of fields. Using these routines, you can easily implement a user interface that displays the database structure (for instance, a pop-up menu listing the tables).
Execute Queries
When you want to update data, you generally select all the data in a table or perform a search to find specific data and create a selection of records. Users can then add, update or delete data in this selection.
There is only one selection of records at a time for each table in each process. This selection of records remains valid until it is changed (e.g., another query is processed).
Use Named Selections
4D Open for 4th Dimension supports named selections, allowing optimum use of your queries and selections. After performing a query or search, you can have 4D Server maintain the resulting selection of records as a named selection. Using this named selection, you can instantaneously retrieve the selection without re-executing the query.
Use Arrays
4D Open for 4th Dimension provides routines for sending and retrieving data using arrays that behave like data buffers.
Manage Multiple Users
You can manage database operations in a multi-user environment by setting the access modes of tables to read/write or read-only, and unlocking records when you are finished with them.
Use Transactions
You can perform complex updates, including those involving multiple tables, while maintaining data integrity. To provide this functionality, 4D Open for 4th Dimension includes routines for starting, validating and cancelling transactions.
Perform Calculations
4D Open for 4th Dimension can help you quickly summarize a set of data by performing numerical calculations, such as the sum, average, maximum and minimum.
Data Security
Clients accessing 4D Server through 4D Open for 4th Dimension are subject to the 4th Dimension password access system. Such clients must provide valid user names and passwords if the database is password protected. Access privileges to records for loading, writing, updating and deleting are also required.
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