Repairing Broken Links
Take a moment to save your map document. From the main menu, select File, then Save. Always give your files meaningful names. Untitled is the default file name for a map document. Never use the default name. Call the map document file, “Humboldt County Maps.” Save the file inside your main workspace folder, GSP101_Activity1.
The most difficult fact for novice GIS users to remember is that a map document file (.mxd) does not store the data layers. To represent the information on the map, it creates a link to the shapefiles or any other data you add to the map document. If the shapefiles get deleted, corrupted, or moved, the map document will no longer be able to display the data on the map. The link to the data gets broken, and ArcMap loses track of the data. To demonstrate this behavior, close ArcMap. Temporarily move your original, working, and final folder to a different folder. If you are working from the desktop, try moving them to the downloads folder. The location does not matter, as long as it is different. The Humboldt County Maps.mxd should now be by itself inside the folder GSP101_Activity1. Double click the Humboldt County Maps.mxd file to open the map document.
The chances are that you will see an empty data frame instead of your map. In the Table of Contents, a red exclamation point appears next to each layer. Because the folder moved to a new location, the links broke.
You can repair the broken link by clicking on the red exclamation point. When the Set Data Source window opens, navigate to the location of the data. You may need to connect to the Desktop to locate the working folder. Select the missing data and click Add. ArcMap should automatically repair the link for the remaining data layers in that folder.
Close your map document and do not save. Instead, return the original, working, and the final folder to GSP101_Activiy1. Then, reopen the map document. Make sure there are no broken links. If you encounter any, be sure to repair them before moving on.
Moving your workspace folder from one location to another is standard practice. To help to avoid broken links, you will change the map document properties. From the Main Menu, select File, then Map Document Properties. Check the box that says, store relative pathnames to data sources. Click OK when you are ready. On the Standard toolbar, click the Save icon. The icon looks like an old fashion floppy disk. This setting allows ArcMap to remember the location of the data sources relative to its current position. Now when you move the entire workspace folder, ArcMap will keep track of the contents.
The store relative paths setting does have some limitations. It only remembers the location of the map document relative to its position to the data. If you move the map document or the data, relative to the current map document location, the links will break again. This means that if you rearrange or move anything out of the project folder, GSP101_Activiy1, then the links may get broken. To safely back up your data, you will have to move or copy the entire project folder, with the subfolders and map document inside.