From Books On Line regarding Start Up Parameters:
"-c: Shortens startup time by starting an instance of SQL Server independently of the Service Control Manager, so that SQL Server does not run as a Microsoft Windows NT® 4.0 or Windows 2000 service.
-m: Starts an instance of SQL Server in single-user mode. When you start an instance of SQL Server in single-user mode, only a single user can connect, and the CHECKPOINT process is not started. CHECKPOINT guarantees that completed transactions are regularly written from the disk cache to the database device. (Typically, this option is used if you experience problems with system databases that should be repaired.) Enables the sp_configure allow updates option. By default, allow updates is disabled. "
I have never had the need to use the -c parameter but I suppose it would give a marginal performance boost to a server that is very busy. It would also make you unable to see or control the Sql Server Service from the Services panel.
The -m is typically used with actions such as performing upgrades or repairing a database to ensure that it is not in use by other people or processes during these types of operations. I hope this answers your question.
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