I got a ticket to create LUNs of different size 30GB,50GB so on and mark it as ASM DISK X (x could be any number). There are different data store in VMware. Lets suppose there is a virtual server 'A' that is running RHEL6, I need to add LUN in this server 'A'. What I did was, there is already data store named,lets say 'qwzzx_104', but I had chosen another data store lets say 'qwxxm_100' and taken 50GB to make LUN and marked it as ASM DISK X (x could be any number). Have I done job correctly? OR the correct way is, to choose the 50 GB from the existing datastore 'qwzzx_104' not from another data store 'qwxxm_100'.

Help me to clear my confusion. Thank you.

One VM can have disks from different datastores. This depends on the purpose of the datastore you used and any business processes that would have prevented you from doing so. Based on what you mentioned, it appears that at least technically, it should be OK.