Collection definitions apply a polling definition to a node.  

They specify the: 

• SNMP index to use (if required).
• The frequency to poll
• The amount of data to keep
• How long to collect for.

Collection definitions can be created/edited/deleted in the GUI and also from the CLI using:

 opcharts-cli.pl

Importing and exporting of collection definitions is also supported using opcharts-cli.pl.  

Note that these include node names so transferring these between servers means the node needs to exist on both servers.