Using the SQL Server Service Startup Options

When you install SQL Server, Setup writes a set of default startup options in the Microsoft Windows registry. You can use these startup options to specify an alternate master database file, master database log file, or error log file.

Startup options can be set by using SQL Server Configuration Manager. For information, see How to: Configure Server Startup Options (SQL Server Configuration Manager).

Default startup options Description

-d master_file_path

The fully qualified path for the master database file (typically, C:\Program Files\Microsoft SQL Server\MSSQL.n\MSSQL\Data\master.mdf). If you do not provide this option, the existing registry parameters are used.

-e error_log_path

The fully qualified path for the error log file (typically, C:\Program Files\Microsoft SQL Server\MSSQL.n\MSSQL\LOG\ERRORLOG). If you do not provide this option, the existing registry parameters are used.

-l master_log_path

The fully qualified path for the master database log file (typically C:\Program Files\Microsoft SQL Server\MSSQL.n\MSSQL\Data\mastlog.ldf).

You can override the default startup options temporarily and start an instance of SQL Server by using the following additional startup options.

Other startup options Description


Shortens startup time when starting SQL Server from the command prompt. Typically, the SQL Server Database Engine starts as a service by calling the Service Control Manager. Because the SQL Server Database Engine does not start as a service when starting from the command prompt, use -c to skip this step.


Starts an instance of SQL Server with minimal configuration. This is useful if the setting of a configuration value (for example, over-committing memory) has prevented the server from starting.

-g memory_to_reserve

Specifies an integer number of megabytes (MB) of memory that SQL Server will leave available for memory allocations within the SQL Server process, but outside the SQL Server memory pool. The memory outside of the memory pool is the area used by SQL Server for loading items such as extended procedure .dll files, the OLE DB providers referenced by distributed queries, and automation objects referenced in Transact-SQL statements. The default is 256 MB.

Use of this option might help tune memory allocation, but only when physical memory exceeds the configured limit set by the operating system on virtual memory available to applications. Use of this option might be appropriate in large memory configurations in which the memory usage requirements of SQL Server are atypical and the virtual address space of the SQL Server process is totally in use. Incorrect use of this option can lead to conditions under which an instance of SQL Server may not start or may encounter run-time errors.

Use the default for the -g parameter unless you see any of the following warnings in the SQL Server error log:

  • "Failed Virtual Allocate Bytes: FAIL_VIRTUAL_RESERVE <size>"
  • "Failed Virtual Allocate Bytes: FAIL_VIRTUAL_COMMIT <size>"

These messages might indicate that SQL Server is trying to free parts of the SQL Server memory pool in order to find space for items such as extended stored procedure .dll files or automation objects. In this case, consider increasing the amount of memory reserved by the -g switch.

Using a value lower than the default will increase the amount of memory available to the buffer pool and thread stacks; this may, in turn, provide some performance benefit to memory-intensive workloads in systems that do not use many extended stored procedures, distributed queries, or automation objects.


Reserves virtual address space for Hot Add memory metadata when AWE is enabled with 32-bit SQL Server 2005. Required for Hot-Add memory with 32-bit AWE, but consumes about 500 MB of virtual address space and makes memory tuning more difficult. Not required for 64-bit SQL Server. Hot Add Memory is only available for Windows Server 2003, Enterprise and Datacenter editions. It also requires special hardware support from the hardware vendor.


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.


Does not use the Windows application log to record SQL Server events. If you start an instance of SQL Server with -n, we recommend that you also use the -e startup option. Otherwise, SQL Server events are not logged.


Allows you to start a named instance of SQL Server 2005. Without the -s parameter set, the default instance will try to start. You must switch to the appropriate BINN directory for the instance at a command prompt before starting sqlservr.exe. For example, if Instance1 were to use \mssql$Instance1 for its binaries, the user must be in the \mssql$Instance1\binn directory to start sqlservr.exe -s instance1.

-T trace#

Indicates that an instance of SQL Server should be started with a specified trace flag (trace#) in effect. Trace flags are used to start the server with nonstandard behavior. For more information, see Trace Flags (Transact-SQL).


Disables the keeping of CPU time and cache-hit ratio statistics. Allows maximum performance.


When specifying a trace flag with the -T option, use an uppercase "T" to pass the trace flag number. A lowercase "t" is accepted by SQL Server, but this sets other internal trace flags that are required only by SQL Server support engineers. (Parameters specified in the Control Panel startup window are not read.)

Using Startup Options for Troubleshooting

Some startup options such as single-user mode and minimal configuration mode are principally used during troubleshooting. Starting the server for troubleshooting with the –m or –f options is most easily done at the command line, while manually starting sqlservr.exe.


When SQL Server is started by using net start, startup options use a slash (/) instead of a hyphen (-).

Using Startup Options During Normal Operations

You may want to use some startup options every time you start SQL Server. These options, such as –g or starting with a trace flag, are most easily done by configuring the startup parameters by using SQL Server Management Studio or SQL Server Configuration Manager. These tools save the startup options as registry keys, enabling SQL Server to always start with the startup options.

See Also


How to: Start an Instance of SQL Server (sqlservr.exe)
How to: Start an Instance of SQL Server (SQL Server Configuration Manager)
How to: Start an Instance of SQL Server (net Commands)

Other Resources

Managing SQL Server from the Command Prompt Using sqlservr.exe

Help and Information

Getting SQL Server 2005 Assistance