Dell R620 Server Idrac appears occasionally unavailable how to troubleshoot

R620 server, the more frequent idrac can not connect, or connect the number of users over the limit, there are several ways to try:
1, upgrade the Idrac card firmware
Download and upgrade the latest 1.57.57 Version of FIRMWARE:HTTP://WWW.DELL.COM/SUPPORT/HOME/US/EN/04/DRIVERS/DRIVERSDETAILS?DRIVERID=XH6FX
This version of bug fix mentions a little:
? Fix for issues this cause iDRAC7 sluggish responsiveness after a prolonged period of time (approx. 45-100 days, depending On the usage). In some cases, if the IDRAC isn't reset, the IDRAC may become unresponsive and requires a server AC power on reset. This issue is introduced in firmware release 1.50.50 and fixed in 1.56.55.

This version resolves a problem that could not be answered after 45-100 days of Idrac startup.

2, kill out the timeout connection session
There are 2 methods:
A. Reboot the BMC card
Execute command: Ipmitool MC Reset Cold, after the BMC Reset, all sessions will reset the release.

B. Killing out a timeout session
If the BMC card is allowed to connect over the network remotely
Ipmitool LAN set 1 access on

or in the following place.
IDRAC set up => service => VNC Server => timeout

Or at the bottom of the Idrac card, set:
IDRAC set => network => IPMI settings => enable IPMI on LAN

It is also recommended that the timeout value of the Web server and SSH service be appropriately lowered:
IDRAC set => service => Web Server => Timeout
IDRAC set => service => SSH => timeout
IDRAC set => service => Telnet => timeout
IDRAC set up => service => VNC Server => timeout

Turn off timeout sessions with the Racadm tool (installation of the Racadm tool) to first view current session connectivity, for example:
[15:41:10-root@fzdm-10-59-xx-xx:~] #racadm-R 10.59.xx.xx-uroot-p "XX" Getssninfo
Security Alert:certificate is invalid? Self signed certificate
Continuing execution. Use-s option for Racadm to stop execution on certificate-related errors.
Ssnid Type User IP address Login date/time
—————————————————————————
SSH Root 10.5.xx.xx 11/18/2014 15:38:43
GUI Root 10.5.xx.xx 11/18/2014 15:40:27
Racadm Root 10.59.xx.xx 11/18/2014 15:41:17
SSH Root 10.59.xx.xx 11/18/2014 15:41:18

Again, close the timeout session connection by executing the following command
[15:40:52-root@fzdm-10-59-xx-xx:~] #racadm-R 10.59.xx.xx-uroot-p "XX" Closessn-i 25
Security Alert:certificate is invalid? Self signed certificate
Continuing execution. Use-s option for Racadm to stop execution on certificate-related errors.
Session closed successfully.