1. A method for program conversion for a network system, comprising: creating a second virtual machine (“VM”) running on a network device in response to a program modification signal; building a second database having a second data structure and a second metadata coded in binary format in the second VM in accordance with requirements relating to a new version of software, wherein building a second database includes establishing a data structure containing a value field, a length field, and an offset field, and activating an in-service software upgrade (“ISSU”) manager and a virtual machine manager (“VMM”) for allowing the second VM running concurrently with the first VM on the network system; accessing a first database having a first data structure in a first VM based on current version of software while the second database is being built; generating binary information for the second metadata in response to a first metadata of the first database, wherein generating binary information for the second metadata includes loading first binary data from the first metadata of the first database and converting the first binary data to second binary data based on the new version of the software, wherein converting the first binary data includes converting the first binary data having a first binary format to second binary data with a second binary format based on the new version of the software; and switching over from accessing the first database having the first data structure hosted by the first VM to the second database having the second data structure hosted by the second VM when a switchover command is received from the ISSU manager.