Product and Software: This article applies to all Aruba controllers and ArubaOS 3.3.2.x and later.
The “RESTARTING ALL TX” message means that the AP is on a DFS channel.
When the AP moves to a DFS channel, it is supposed to wait for 1 minute (or 10 on some channels in ETSI) before beaconing. "Restarting all tx" gets printed after the initial non-occupancy time expires.
You can get additional messages, similar to the following, if you have ap-debug configured:
May 12 08:55:52 sapd: <404070> |AP Test-00:0b:86:c6:5f:email@example.com sapd| AM 00:0b:86:c5:f1:a0: ARM Empty Channel Trigger new 60-0/0 old 36-0/2 new_rra 60/2
May 12 08:55:53 KERNEL(Test-00:0b:86:c6:5f:firstname.lastname@example.org): DFS REQUIRED FOR 5300, STOPPING ALL TX <<<< here 5300 Mhz means channel 60
May 12 08:56:53 KERNEL(Test-00:0b:86:c6:5f:email@example.com): RESTARTING ALL TX