Copying Data between Databases

• Data Transfer

  The Data Transfer utility (RECASTDB) copies data from the source database to the target. This facility is described in Transferring Data

  • You can transfer data by name where fields and tables may have non-matching internal numbers

  • You can choose to delete data that is not on the source database

  Use the Data Transfer utility if you wish to transfer data between databases that have the same structure and are on the same system

• Data Export and Import

  The Report Writer and Importer utilities (REPSETUP, REPPRINT, IMPSETUP, IMPPOST) are used to transfer the data. This facility is described later in Exporting Data with Report Writer and Importing Data using a Parameter Set.

  The Data Export and Import facility uses the internal reference numbers of tables and fields to transfer data. If this proves unsuccessful, use the Data Unload and Load facility which transfers data by name

  The Data Export facility will only create lines in the export file up to 500 characters in length, and to creaet longer lines you need to set yo a print device that does not put mew liens between lines. If you have created an export file by other means, you can use an Importer program to import it as long as it conforms to the format described in Understanding Field Groups later in this section. In this case, there is no practical limit on the length of lines; they may hold up to 8190 characters

  The data export and import process may be summarised as follows:

  1. On the source database, create the export program with Report Writer

  2. Export the data from the source database to an ASCII file by running the export program

  3. Extract the export program to a file with Report Writer

  4. Post the export program to the target database with Report Writer

  5. Automatically generate the importer program, from the export program, on the target database

  6. Import the data from the ASCII file to the target database by running the Importer program

  Automatic facilities are provided to help you produce the export and import programs quickly and easily

  On export, you can choose to extract records, depending on conditions.

  On import, you can choose whether:

  • To allow records to be inserted that are not already on the target database
  • To allow records to be updated that are already on the target database
  • To force parent checking or parent verification to prevent a record from being posted to the target database when it fails the check. These checks are rarely, if ever, needed
  • To check that foreign keys are the same, and prevent posting if not
    
    

  You can also specify processing for import fields.

  Use the data export and import facility if you wish:

  • To copy data between databases with a different structure
  • To transfer the data to a target database on another system
  • To exchange data with another database system, or application, such as a spreadsheet or mail merge.
    
    

• Data Load and Unload

  The data Unload utility (UNLOAD) exports data from selected tables to an export file. The data Load utility loads data from the export file into the target database. This is a simple two stage process without the line length limitation of data exporting and importing

  The data transfer is by name. This allows the data to be loaded where tables and fields have the same names but different internal numbers

  As with the Data Export and Import facility, use the data Load and Unload facility if you wish to copy data between databases with a different structure. This new facility is provided as an alternative to the Data Import and Export facility

  You can also use the Load utility to import data that originates on a non-DP4 system, if you format the ASCII file exactly as explained in Transferring Data with the Load and Unload Facility