What are the possible ways of exporting layout to a text file and importing it back while retaining layout and pcell properties

Hi, 

I wanted to ask what are the different possible ways of exporting the layout to a text file and then importing it back while retaining the layout instances properties and the pcells

I came across "dbWriteSkill" but I am not sure what is meant by t_release -> The release in which the file will be loaded

then there is also "dbDumpPcDefinePcell" and "pcSkillGen" I am not sure what is the difference compared to the dbWriteSkill and which one to use 

I need this to modify export and compare layouts from different PDKs and then modify them accordingly, I have considered using skill directly to do the comparisons and the modifications but there are multiple limitations blocking this approach 

virtuoso version ICADVM20.1-64b

sub-version ICADVM20.1-64b.500.28.EHF13629

Thanks, 

Fahmy