i made whole transforms.conf and prop.conf for a data in splunk and analyse FORMAT in transform.conf with $0 and without it but nothing changes had reflected
According the transforms.conf documentation:
_meta : A space-separated list of metadata for an event.
Honestly I dont get your question, but I advice you to visit the documentation for transforms.conf. It has a lot of examples, which can help you. If not feel free to clarify your question.
Please share your transforms.conf and props.conf settings.