pg_xlog_archive folder size is very big While doing DB operations on PostgreSQL pg_xlog_archive is consuming more than 150GB disk space with the option "archive_mode = on". How to cleanup/reduce pg_xlog_archive folder size.

What will happen if I disable "archive_mode= off". I have tried "off" option also but DB operations are taking too much time. How archive_mode do work?
A WAL archive can be used for disaster recovery, PITR (point in time recovery), or as part of a replication set up.  If you don't know why you set it up in the first place, then maybe you don't need it.  The consequences of turning it off is that you can't use that type of disaster recovery, can't do PITR for after the time it was turned off, and can't use that kind of replication anymore.

Also, note that WAL often compresses extremely well, often 25 fold or more, with something like "xz" or "lzip". So if you mostly concerned with storage, you can implement compression.