You can clean up your drawing by removing unused items in your drawing such as unreferenced layers, blocks, and style definitions.
The term, purge, is used to describe removing a definition rather than erasing an object. For example, erasing all objects that use a dashed linetype still leaves the linetype definition in the drawing. Similarly, erasing all block references to a fixture still leaves the block definition of that fixture block in the drawing.
A drawing that has the minimum number of unreferenced definitions open, save, and perform faster, and use less memory. In addition, purging a drawing provides the following specific benefits:
You might want to consider exceptions to purging to maintain standardized definitions for future work.
In some cases, it might seem that you should be able to purge an item, but you can't determine exactly why the Purge dialog box doesn't allow it. Here's a list of the most common reasons why an item can't be purged:
The Purge dialog box provides you with all the details about an item and why you cannot purge it from your drawing. Specifically, you can click Non-Purgeable Items and examine the Details section to find the key information you need. You can click Select Objects to navigate to the non-purgeable object and take appropriate action to make it purgeable.
The Purge dialog box also provides you with a thumbnail preview of the item selected in the tree view pane for a visual representation of the item.