As part of Oracle’s efforts to improve the user access experience, "scan" is introuduced in the latest release of its RDBMS, namely, Oracle 11gR2, to replace the current "vitrual" service name which needs to be set up by a DBA through some relatively tedious configuration and test procedures. With "scan" in place, Oracle will automatically connect its users to the available and less used instance in a RAC environment to offer the best availability and load-balancing.
Demand from the OS side, however, comes along with this new and exciting feature. And following explains how a Linux (RedHat, version 5 or higher) Administrator sets it up:
1) Log into Linux as root, and edit the file /etc/sysconfig/ntpd. Generally, it looks something like:
# Drop root to id ‘ntp:ntp’ by default.
OPTIONS="-u ntp:ntp -p /var/run/ntpd.pid"
# Set to ‘yes’ to sync hw clock after successful ntpdate
# Additional options for ntpdate
2) Modify the file to add the "-x" option to ntp
OPTIONS="-x -u ntp:ntp -p /var/run/ntpd.pid"
3) Restart the daemon:
# service ntpd stop
Shutting down ntpd: [ OK ]
# service ntpd start
ntpd: Synchronizing with time server: [ OK ]
Starting ntpd: [ OK ]
# ps -ef |grep ntp
ntp 32051 1 0 10:48 ? 00:00:00 ntpd -x -u ntp:ntp -p /var/run/ntpd.pid