Will changing the permissions of /var/mqm/ on mq server effect any application connectivity. recently have changed the permissions to 770 for /var/mqm/ one of the applications which is running on the same server had issues to consume the messages on the queue.
Application which are using client connections did not face any issues.
need some help to understand what went wrong
Local applications connecting in binding mode need read access on some files and might even need write access in some directories. This is all documented here.
This is law: Don't change file permissions in /var/mqm, they have been carefully selected.
In case you have altered permissions recursively, I guess it is a considerable effort to restore the original setting. If you have tried out in a test environment (I hope), thus loosing messages may not be a big deal, then simply restore the file system from your backup (just kidding) or reinstall MQ and recreate the Queue Manager. If it is production, you may try to restore permissions based on a reference installation.