Thanks a lot friends, your replies have been very helpful.

The table is not partitioned because we use SQL Server 2008 standard so this version does not have partitioning feature. I don't really know what 'Partition = ALL' means as i am new to SQL Server. I will be reading through this parameter now.

I am thinking to avoid the SORT_IN_TEMPDB option unless it could be of a great help (performance perspective)?

This table is 400GB in size, has 9 indexes which are approx. 200 GB in size. The fragmentation is pretty high on all these indexes (>50) that's why i choose to rebuild them.

i am quite happy to know that these statements will run in sequence so that means after one statement completes the next will start right? (sorry if i am repeating my question again)

Managed to find a 10 hour window to run the rebuild job so there will be no user activity at this time and server is fully available for maintenance.