External database links are most appropriately used when data is dynamic in nature. For example, a sewer pipe may have several instances of maintenance. This is an ideal situation in which to use an external database link. The object has a single key, which is related to a record in a database. The database application can then be used to relate this record to other tables that contain additional information.
Some of the common benefits of using external tables:
1. External data can be accessed by individuals without their having access to the drawing files.
2. External data is better for data that changes frequently, such as maintenance information.
3. Drawing file size is not increased if the data is stored externally.
When you drag and drop a database file into the AutoCAD Map 3D Explorer task pane to attach it to the drawing, a Universal Data Link (UDL) is automatically created. By default, it is stored in the folder called Data Links in the Application Data folder in the users Document and Settings folder.
Monday, December 1, 2008
AutoCAD Map 3D: Drawing Cleanup Guidelines
When performing drawing cleanup, consider the following issues:
If objects have object data, hyperlinks, or SQL links associated with them, drawing cleanup may break these associations. You can control this behavior by selecting a cleanup method that either retains or modifies the original object.
For greater control of the cleanup operation, consider performing one cleanup action at a time and completing one action before moving to another.
To display the extent and nature of the problems in the drawing, use markers for your first cleanup pass.
Start the cleanup operation using small tolerances and review to find out whether the tolerance setting has captured the errors. If the tolerance settings are too low, repeat the cleanup operation with a larger tolerance until the operation recognizes the errors. Be careful when increasing tolerances. If tolerances are set too high, valid geometry can be recognized as errors.
If objects have object data, hyperlinks, or SQL links associated with them, drawing cleanup may break these associations. You can control this behavior by selecting a cleanup method that either retains or modifies the original object.
For greater control of the cleanup operation, consider performing one cleanup action at a time and completing one action before moving to another.
To display the extent and nature of the problems in the drawing, use markers for your first cleanup pass.
Start the cleanup operation using small tolerances and review to find out whether the tolerance setting has captured the errors. If the tolerance settings are too low, repeat the cleanup operation with a larger tolerance until the operation recognizes the errors. Be careful when increasing tolerances. If tolerances are set too high, valid geometry can be recognized as errors.
AutoCAD Map 3D: Drawing Cleanup Strategies
Drawing cleanup is not a single operation in which you remove all errors in the drawing. Depending on the number and type of errors, drawing cleanup is an interactive process in which you clean certain errors and then repeat the process to clean additional errors.
The reason for cleaning a drawing can influence how you approach the cleanup. For example, if you intend to use the drawing for a street network topology, then crossing objects can be tolerated and may even be desirable. However, if you intend to use the drawing to produce a polygon topology, crossing objects cannot be tolerated. You also need to consider any object data or SQL links that are attached to objects in the drawing. Using incorrect methods of cleanup may destroy these links.
The reason for cleaning a drawing can influence how you approach the cleanup. For example, if you intend to use the drawing for a street network topology, then crossing objects can be tolerated and may even be desirable. However, if you intend to use the drawing to produce a polygon topology, crossing objects cannot be tolerated. You also need to consider any object data or SQL links that are attached to objects in the drawing. Using incorrect methods of cleanup may destroy these links.
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