The article describing the external (fast) search index is located here.
Limit the number of parallel threads
Each modern computer has several processors, the high search speed is reached by iterating data in parallel threads on different processors. Best performance may be achieved when the catalog file and the search index are located on SSD drives.
When the catalog file is stored on slower drives, especially on optical drives (DVDs, CDs), or shared in a local network and accessed via a slow network connection, the high number of parallel threads may cause the search index to work slow because of low disk speed. In that case, you may want to limit the number of parallel threads to 2 for slow network drives and slow external hard drives or to 1 for optical drives.
Mark or unmark the "Use external search index" checkbox to enable or disable the external (fast) search index.
If the external search index was not previously created, and you turn it on, the index will be created when you click the OK button.
If the external search index exists, but you turned it off, all files will be deleted from the disk and WinCatalog will perform searches using the catalog file only (works slower than using the external search index).
If you have several catalog files, you may want to use the same settings for all files. Save these settings as default values for new catalog files. By default, when you create a new catalog file, WinCatalog will turn the external (fast) search index on and will not limit the number of parallel threads. Changing the settings and applying them as default values for new catalog files changes this behavior. Saving this configuration will not affect any other existing catalog file.
