How many HD programs can I record and watch simultaneously

And the one I'm watching can be different than the 3 that are recording? Right?

Thanks for the prompt reply.

Yes.

With U-verse you have 4 live streams that can be used to watch and/or record live TV.

The WAN Profile represents streams into the RG,  In your case, you can watch 4 live HD channels at the same time.

The Ingress Profile represents streams into the DVR.  You can record 4 programs at the same time.  In your case, up to 3 of those recordings can be on HD channels.  When recording 3 HD channels, you can watch a 4th live HD channel on a TV connected to a non-DVR STB.

The Egress Profile represent streams out of the DVR to the non-DVR STB.  You can watch 3 previously recorded programs at the same time on TV's connected to non-DVR STB's.  Up to 2 of those recorded programs can be in HD.

Does the Gateway need to be rebooted for a Profile Change to Take effect?

If you are referring to a WAN, Ingress or Egress Profile change, the DVR/STB would need to be rebooted.  You should not need to reboot the RG.

I recently got U-Verse with the Total Home DVR.  Last night, I was recording three HD channels and tried to watch a 4th HD channel.  The TV would not allow me to go to the channel and said the maximum number of HD channels had been reached.

It sounds as if you're saying that if I had another TV that had only a set top box (not the DVR), I could have watched the 4th HD channel on that TV.  Also, if I wanted to record 4 channels, only three of those could be in HD.  Are both of those statements correct?

@BonnyS- It is kind of complicated - there is a limiting factor on what comes into your house based on distance from the VRAD.

First - look in menu- options - system options - sys info - sys resources -streams What does that say? & also egress profile

Given the date of this post is 5 tears old, has the number been increased to match or beet Comcast/X1?

While Uverse still supports a limit of 4 streams, Gigapower customers can have up to 6.

https://www.att.com/esupport/article.html#!/u-verse-tv/KM1040899