This article discusses the “Include Sub-folder” setting that was introduced in SOLIDWORKS 2017 and the performance issues that are currently surrounding it.
If you have upgraded to SOLIDWORKS 2017 and have file locations listed in Reference Documents, you may have noticed significantly, long loading times when opening your files. If the issue did not occur in previous versions of SOLIDWORKS and you have added the same Reference Documents paths at Tools > Options > System Options > File Locations, then this issue may be due to the new options introduced in SOLIDWORKS 2017, the "Include Sub-folders" setting located at Tools > Options > System Options > External References.
So, what is the background to this feature introduction in SOLIDWORKS 2017? According to this help file, SOLIDWORKS conducts a recursive, twelve step search process, which includes searching through Reference Document file locations and their sub-folders, before prompting you to manually browse for the file.
However, the enhancement request SPR #60258 indicates that sub-folders of the Reference Document file locations are not searched recursively for files as it should. It appears that in SOLIDWORKS 2016 and previous versions, the search process only looks into the specified folder listed in the system options. This created the inconvenience of needing to list all sub-folders.
To mitigate the issue, SOLIDWORKS 2017 introduced the new option, "Include Sub-folders". This was intended to help users list less file locations to assist the software in finding assembly components that had alternative saving locations than the assembly or other components. The option is checked by default.
Unfortunately, this new addition has been causing performance issues, particularly when opening files, as indicated in bug report SPR #989453. This SPR has been addressed in 2017 sp4.1 by disabling that "include sub-folders" option by default rather than enabled so it behaves like previous versions by default.
To workaround the issue, you simply need to un-check the "Include Sub-folders" option. If you have sub-folders in your Reference Document file locations, you will need to include them as a new file location in the options. Or upgrade to a version newer than 2017 sp4.1 and the option will be disabled by default.
There were also 2 bugs fixed in 2018 sp1 with this new feature that slowed open times even when no sub-folders existed in a referenced document file location. Those were SPR 1043543, and 1044664.