URLSelectSkipLock, indexer sends a LOCK TABLE url SQL query when fetching a set of new crawler targets from a MySQL database to avoid multiple indexer instances crawling into the same URLs. Fetching targets can take up to a few seconds in a huge database and can make simultaneous search queries stall and wait for indexer to finish fetching targets. URLSelectSkipLock helps to avoid this kind of delays in search queries when you're running only a single instance of indexer at the same time.
Note: Running a single indexer instance with multiple threads using the
-Nswitch is OK together with URLSelectSkipLock yes.
The default value is no.