Distributed Databases

It is sometimes necessary to split a project between different geographical locations, directories, disks or even machines. All links between the portions of the project are maintained. There are three ways in which a project may be split. These are:

• During its creation

• By copying

• By moving the relevant databases.

Example

Assume there is a network of computers, including two known as PC1 and PC2.

PC1 is the server and as such holds the AVEVA base product software. In addition to this it also holds the System database for a project called ABC000. Directory ABC000 contains the project’s database files, for example, ABC001 to ABC011. Let us assume the user wants to move database ABC002 to computer PC2’s disk. Before we can move the database we must create a directory for it on the target machine, PC2. The name given to this directory is not important, but should follow some sort of naming convention. What is important is the name given to the environment variables which show the location of the database.

To work out the required variable name, take the three letters of the project name and append the area code to allocate to the target directory. There is no significance in the numbering used for these areas, although sequential numbering helps the user to remember areas already used.

Note:
The area number must be in the range 1-999.

For example:

Project Name = ABC000
Area Code = 500
Environment Variable name = ABC500

For example:

To specify that the area ABC500 is on drive d:

set ABC500=d:\pdmsproj\newarea

Note:
Environment variable names (ABC500 in the above example) must be in uppercase characters.

When selecting an area number, it is suggested that a number much higher than the number of available databases is used.

Areas can be listed using the LIST AREA areano command, which gives a list of the databases in the specified area.

Once the user has created the area and set the environment variable for it, they can create or move a database to the area by setting the Area Number on the Create/Modify Database window (to 500, in this example).

Clicking System next to the gadget will reset the area number to the system default (0).