Hi Devendra,
I hope here is the information you want.
Chapter 13: Backing Up and Restoring User Databases
--------------------------------------------------------------------------------
Improving dump or load performance
When you start Backup Server, use the -m parameter to improve the performance of the dump and load commands by configuring more shared memory for the Backup Server. The -m parameter specifies the maximum amount of shared memory used by the Backup Server. You must also configure your operating system to ensure that this amount of shared memory is available to the Backup Server. When a dump or load operation completes, its shared memory segments are released.
Configuring additional shared memory improves dump and load performance only if the performance limits of the hardware setup have not been reached. Increasing the value of -m may not result in improved performance when dumping to a slow tape device such as QIC, but it can improve performance significantly when dumping to a faster device, such as DLT.