The best project management organizations and companies out there understand that projects compete for resources, and they plan accordingly. They have governance bodies that weigh the importance of one project versus another, and they have an elaborate ranking system for establishing the priorities of projects so that everyone can see clearly what project comes first when there are resource bottlenecks. The PMO usually works very closely with these organizations to keep their projects running well.
What about operations? How does this fit in?
The reality of most companies is that they do not have seperate project-based resources versus operations-based resources. Major operational initiatives and problems can derail your project quickly. An over-abundance of projects can rob Operations so thoroughly that needed maintenance is ignored, and your operations deteriorate (just ask the american government about this). Major operational problems clash with major project initiatives. Huge political battles can ensue, creating inaction as people who need to do do the work in question instead go sit in meetings waiting for a decision on which work to do. People end up making decisions on an island at times, just picking a direction based on their own personal knowledge rather than wait on the corporate machine to find a direction.
Rather than get lost in these situations, get a grip on your Operations. Include them in the resource planning process. Most importantly, include them in your prioritization process. Is the most important project in the company more important than maintenance of the most important existing product? What about the fifth most important product? The fifteenth? Which customers’ business is more important than your projects? Customer problems can just as easily steal resources. Not all of your customers will be more important than the development of your company’s future either. You have to count them as part of your prioritization process, and you have to make hard decisions like this.
Doing this type of process is hard. It is also vital to your company’s ability to react quickly and decisively to the unexpected. You, and more importantly, your team, need to understand and agree on what comes first.