Merging using SSMS

Before merging partitions, first copy the data filter information (often, the WHERE clause for filters based on SQL queries). Later, after the merge is completed, you should update the Partition Source property of the partition containing the accumulated fact data.

• In Object Explorer, expand the Measure Groups node of the cube containing the partitions that you want to merge, expand Partitions, right-click the partition that is the target or destination of the merge operation. For example, if you are moving quarterly fact data to a partition that stores annual fact data, select the partition that contains the annual fact data.
• Click Merge Partitions to open the Merge Partition <partition name> dialog box.
• Under Source Partitions, select the check box next to each source partition that you want to merge with the target partition, and click OK.
• Right-click the partition containing the accumulated data and select Properties.
• Open the Source property and modify the WHERE clause so that it includes the partition data you just merged. Recall that the Source property is not updated automatically. If you reprocess without first updating the Source, you might not get all of the expected data. 

Source partitions are immediately deleted after the source is merged into the target partition. Refresh the Partitions folder to update its contents after the merge is completed.