From http://msdn.microsoft.com/en-us/library/ms175318(SQL.90).aspx:

You can merge partitions in an existing Microsoft SQL Server 2005 Analysis Services (SSAS) database. The ability to merge partitions can be a powerful option, but care must be taken to fully understand both the process of merging and ways to make sure that the merge operation produces your intended results.

To make sure that partitions can be merged at a later time, when you create the partitions, you must consider certain restrictions on merging partitions. Partitions can be merged only if they meet all of the following criteria:

• They are in the same cube.
  
• They have the same structure.
  
• They have the same storage modes.
  
• They contain identical aggregation designs.

mauryakamal wrote   Thanx.. cutely  But we have some query as mentioned below. 1. Same Storage modes means all the partitions are in same storage modes i.e. if we have two storage mode partitions i.e. MOLAP and ROLAP then we can not merge it. (Is it correct) - That is correct as far as I understand. 2.Identical aggreations mean if we have one partitions have 20% aggreation and other partitions have 30% aggreations then also we can not merge it both partitions should be either 30% or 20% aggreations.(Is it correct) - That is correct as far as I understand. 3. what is the meaning of the same structure can you please elaborate it. - The partitions must all have the same dimensions and the same measure groups. 3.Whether we have partitions merging options in BIDS development tool if not then how we can do it.(Please explain it) - Merging is done in SSMS. http://msdn.microsoft.com/en-us/library/ms175640(SQL.90).aspx Thanx in advance. kamal maurya

See my comments in the quoted text above.