Don't DELETE FILES. If CAR is installed or was ever installed, you can purge the CDR records and the CAR stuff that way.
You can also write an SQL script to delete records, probably compact the databases, etc.
You can also have SQL backup the CDR and CAR files (use Enterprise manager) to put them on another server in case you need them.
PURGING the files as described above will make your DMA file MUCH smaller and quicker to migrate.
Also make sure detailed tracing is not turned on. You can also adjust the trace files settings to less files and less size per file. You MIGHT be able to delete some trace files (if done properly,) but I'm not going to sanction that.
