A few questions

I’ve searched the forums looking for answers, but am still not clear on a few things:

1. I see that it is recommended not to have thread names longer than 15 characters, not to have process names longer than 9 characters, and to also use only lowercase for naming.  Can someone explain the reasons for each of these restrictions and the consequences for violating these rules.  Currently, virtually all of our thread names have mixed case, and some are longer than 15 characters.

2. What is the vista.taf file?  What does it contain?

Thanks in advance.