Optimizing your Pro Tools system is yet another important part of having smooth and stable recording / mixing / mastering sessions and each particular process requires different configurations.
Optimizing for recording: When recording audio, latency is a big issue, you want the least latency possible so that there is no lag between the source and what you're capturing, latency issues can cause artifacts in the recording that are not very pretty !
(Assuming you're already inside PTD / LE) Go to the "System" Menu and select "Playback Engine." Here, you will see various options, the first one being H / W Buffer Size. This means: "Hardware Buffer size" which refers to the timing of latency between the hardware and the software. You will notice there are quite a few options in the dropdown menu:
As I said, you want the lowest option your system can perform, if your system can utilize 64 ms latency, fantastic, if not, do not stress yourself too much. If you can keep your buffer size between 64 and 256, you're doing well. If you're uncomfortable playing with these settings for now, that's fine! Those of you who fall into this category, just keep it at 512 samples.
The next option that you will see is: "Host Processors" This indicates to how many processors Pro Tools will use to allocate threads to. If you have a quad core CPU, you will be using four cores, if you have hyperthreading enabled in your BIOS settings, you will see 8 in this menu, if you have 8 physical cores (dual CPU) you will see 8 and if you 're using hyperthreading with 8 physical cores, you will see 16! If you're using 8 physical cores though, you will not have any need to enable hyperthreading. Basically, for this particular option, keep it as high as you can, the manual will say to use one less core, but I disagree.
The final setting under the "Settings" category is CPU usage limit, what this is, is basically a brickwall limiter for your CPU that works off of a percentage. When your system reaches a specified usage amount due to RTAS plug ins and Audiosuite rendering, etc, once it reaches the peak, it will go no further than that. A setting of 85% or 90% is acceptable here.
The next section you will see refer to the DAE playback buffer, which deals with disk latency and plugins / audio streaming. This is a very important setting for recording and mixing. Different from the H / W buffer in that this setting does not focus on the CPU or Digidesign hardware, but on your hard drive. You will see "size" and in the dropdown menu you will see levels 1-4, keep this on level 1 and if your system can handle it, put it on 0! For Cache size, leave this on normal without your system is really having a hard time, then switch it to large. (If you followed my recording PC guide, you will be just fine leaving this on normal!)
Lastly, you will see an option with a tick box that says: "ignore errors during playback / record" (may cause clicks and pops). This setting is debatable, if there is something wrong and you keep getting errors when mixing about the DAE engine and you just can not get it to go away, tick this box (especially with the 8.0.3 update) I hear no clicks or pops with or without it. I have not had this particular option enabled when tracking so I can not speak for this option in such an instance, only with mixing.
Try to keep it unchecked if possible, if you notice nothing wrong with tracking or mixing, leave it on, it is most likely doing no harm.
These steps should lead you in the right direction for a stable recording system with Pro Tools HD / LE!