Change in Series group in CIN

Hi Experts

Our company has 2 plants P1 & P2 and 2 seperate Excise registers , excise groups and series groups are maintained for both plants.

Now we are clubbing P1 plant into P2 and hence forth any excise invoice generated specific to plant P1 should have the same series as plant P2.

Pls suggest What changes are required for generating the same series Excise invoices for plant P1 similar to plant P2 since plant P1 now got merged with P2

Rajiv