If you’ve ever messed around with IBM Rational ClearCase, you’ve probably hit that point where you’re staring at an error that basically says, “Nope, you don’t own this branch, so good luck.”
That’s where Chmaster comes in. It’s one of those commands that doesn’t look fancy but can make or break your workflow when working with multiple replicas.
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What Exactly Is Chmaster?
In ClearCase, every branch type or element has a “master.” Think of it like ownership. Only the replica that owns it can make changes.
So if you’re trying to tweak something that your site doesn’t “own,” you’re stuck… unless you use Chmaster.
This command changes the mastership of an object (like a branch, label, or element) to a new replica. Once you run it, the new replica is in charge, and you can finally move forward.
Real-World Example
Here’s one I ran into: we had dev teams split across the US and India, each working on their own replica. One team needed to fix a bug on a branch that technically “belonged” to the other side.
Without Chmaster, we’d have been blocked until someone overseas woke up and pushed the change. Instead, we just transferred mastership, handled the bug locally, and kept moving.
Not glamorous, but it saved us hours.
Why Most Guides Miss the Point
If you Google around for Chmaster, most of what you’ll see is dry syntax dumps. Like:
cleartool Chmaster –nc –replace brtype:branch1@/vob/proj vobtag
Cool, but it doesn’t tell you when to use it or why it matters. The reality is:
- It’s all about collaboration. Multi-site setups need Chmaster so teams aren’t bottlenecked.
- You have to be careful — switching mastership back and forth too often creates chaos.
- Documentation buries real use cases under walls of syntax.
Things to Keep in Mind
Before you go wild with Chmaster:
- Plan ownership. Randomly flipping masters is a recipe for confusion.
- Sync first. Always replicate updates before switching masters, or you risk conflicts.
- Audit later. Track who owns what after changes, so nothing gets lost.
If you want the official breakdown, IBM still has a solid reference page on ClearCase commands (here’s their ClearCase Command Reference). And if you’re newer to the whole topic, Wikipedia’s page on IBM Rational ClearCase is a decent starting point for context.
My Take
I’ll be honest: Chmaster is not the kind of command you’ll use every day. But when you do need it, you’ll be glad it exists. It’s the “unsung hero” of ClearCase invisible until you’re stuck at 2 a.m. with a build that won’t move forward.
Bottom line? Chmaster keeps distributed teams from tripping over replica ownership. If you’re in a multi-site setup and haven’t used it yet, you probably will someday.