The -P parameter for Backup Server configures the number of service threads Open Server creates.
The maximum number of service threads is 12,228. The minimum value is 6. The maximum number of threads equals the maximum number of stripes available. If you have started Backup Server without setting a high enough -P value, and you attempt to dump or load a database to a number of stripes that exceeds the number of threads, the dump or load operation fails.