If HAD is periodically killed by GAB for no apparent reason, review the HAD core files for any DNS resolver functions (res_send(), res_query(), res_search() etc) in the stack trace. The presence of DNS resolver functions may indicate DNS configuration issues.

The VCS High Availability Daemon (HAD) uses the gethostbyname() function. On UNIX platforms, if the file /etc/nsswitch.conf has DNS in the hosts entry, a call to the gethostbyname() function may lead to calls to DNS resolver methods.

If the name servers specified in the /etc/resolve.conf are not reachable or if there are any DNS configuration issues, the DNS resolver methods called may block HAD, leading to HAD not sending heartbeats to GAB in a timely manner.