An IRC channel is a shared space: everyone can see what everyone else is saying. Normally, this is a good thing, as it allows people to jump into a conversation when they think they have something to contribute, and allows spectators to learn by watching. But it becomes problematic when someone has to provide a large quantity of information at once, such as a debugging session transcript, because pasting too many lines of output into the channel will disrupt other conversations.
The solution is to use one of the pastebin or pastebot sites. When requesting a large amount of data from someone, ask them not to paste it into the channel, but instead to go to (for example) http://pastebin.ca, paste their data into the form there, and tell the resulting new URL to the IRC channel. Anyone can then visit the URL and view the data.
There are a number of free paste sites available now, too many for a comprehensive list, but here are some of the ones I've seen used: http://www.nomorepasting.com/, http://pastebin.ca/, http://nopaste.php.cd/, http://rafb.net/paste/, http://sourcepost.sytes.net/, http://extraball.sunsite.dk/notepad.php, and http://www.pastebin.com/.