Help on audit.log

Dear Team,

I need a help on understanding the audit.log file on Linux servers.
I can see the audit logs under /var/log/audit/ folder and a configuration file for that in /etc/audit/auditd.conf

What actually getting recorded in audit.old file, Is the same information in /var/log/secure and other log files.
What is the distinct feature of this log file.

The reason for bringing up this question is we have a concern audit log message getting filled up and hungs the servers with the below message.

kernel: audit: audit_backlog=65537 > audit_backlog_limit=65536
kernel: audit: audit_lost=126533574 audit_rate_limit=0 audit_backlog_limit=65536

So is that really audit.log is nescessary or Can I stop the auditd process and get the details from other logs like messages/secure.

Please help, Thanks.