Hi sparc200
U can't convert .DB format into .VOLCANO format,
As you know magma cannot read .DB file or Synopsys tools cannot read .Volcano format,
They are company owned cutomized format for thier respective tools,
SO from the given details, i can infer that u want ot P&R for the Netlist generated by the DC,
so what i can suggest is to generate the Verilog or VHDL netlist from DC,
Then take the corresponding library file that was targetted for the the NEtlist,
The library file for Volcano preparation in MAGMA are .LIB , .LEF or .GDS and corresponding Technology rules given by the foundry, follow the rules given in the MAGMA apllication notes for Library preparation
and then u import the netlist form DC into MAGMA design environment and u follow the P&R for the netlist,
Hope this will help you,
Regads,
au_sun