You may see this error message for a variety of reasons where cache generation has been terminated or not completely successful. The following are some of the most common scenarios where you may see this message:
- Ran out of memory
- One or more instances terminated for unknown reason
- One or more SOC machines went down or not accessible
- SDE connections or other references to data (disk drives or shared network drives) went down
Rerun the tool with appropriate options to pick up the cache generation where it terminated. For example, consider the option to generate only empty tiles to avoid deleting all tiles and re-creating the cache from scratch. Also, consider caching map services using feature class extents with the status reporting option such that you can rerun the tool by skipping the features in the feature class that completed cache generation without any errors. It is also a good practice to examine server log files for any errors. The log files are located at <ArcGIS Server Installation directory>\server\user\log on the SOM machine.