WLM
Workload Manager: the part of z/OS that decides which work gets the processor, memory and disk access first, based on goals the site sets.
Also written Workload Manager, service class, service definition, classification rules
WLM, the Workload Manager, decides how z/OS shares its resources between all the work that wants them. A mainframe runs online transactions, batch jobs and system tasks at the same time, and WLM decides who gets the processor first when they compete.
The site does not set priorities directly. Instead it writes goals in a service definition. Work is sorted into service classes, and each class has a goal, such as "90% of these transactions finish in half a second", and an importance from 1 (most important) to 5. Classification rules decide which class a piece of work belongs to, for example by job class, transaction name or user.
Every few seconds, WLM checks whether each class is meeting its goal and moves resources towards the important work that is missing its goal. That is why a busy system can keep online banking fast while a large batch job runs more slowly in the background.
As a developer or operator, you mostly meet WLM when work runs slower than expected. The question to ask is which service class the work is in, and what its goal is.
Where can I learn this hands-on?
Right here, at ZedBank. You take a junior job at a simulated bank and learn each part of the work by doing it, with Zed beside you. There's nothing to install.
Start at ZedBankRelated
- z/OSThe main operating system that runs on IBM mainframes, in the same way Windows or Linux runs on a laptop or server.
- Address spaceAn isolated pocket of memory in which a program runs, so that one program cannot interfere with another.
- Job classA single-character label on a job that tells the system what kind of work it is and how to schedule it.
- Batch processingRunning work in bulk, without anyone watching, usually on a schedule. The overnight run that settles a day of transactions.
- Online transaction processingHandling many small pieces of work in real time while someone waits: a card payment, a balance check, a seat booking.
- SysplexA group of mainframe systems joined together so they behave as one, sharing work and data so that no single failure stops the service.