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 and how long to collect for.
Collection definitions can be created/edited/deleted in the GUI and 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.