① Explainer · Licensing concept
Adding a new application to an existing LPAR normally lifts the peak that prices everything else on it. zCAP breaks that link: the new application runs collocated but is priced as if it had its own LPAR. Here is the mechanic, with the MSU worked through.
Collocate the application but not its cost. zCAP lets a new workload share an LPAR while being metered as though it ran alone.
z Systems Collocated Application Pricing (zCAP) is an IBM sub-capacity pricing approach for new z/OS applications. Normally, dropping a new application into an existing LPAR raises that LPAR's rolling four hour average, and because the other middleware on the LPAR is priced on that same peak, the new application quietly inflates the bill for everything around it. zCAP removes a large share of the qualifying application's processor time from the utilization reported for that other middleware, so the application is priced on its own footprint rather than piling onto the shared peak.
The reported reduction is commonly up to 100% of the new application's general purpose processor time for other middleware, and up to 50% for z/OS itself. To qualify, you need sub-capacity pricing under AWLC, AEWLC, or zNALC terms on an eligible machine, a genuinely new application, and a zCAP Defining Program: the IBM middleware such as CICS, Db2, IMS, MQ, or WebSphere Application Server that manages the application's processing. The defining program is what lets SCRT attribute the work separately. The worked example shows the difference between collocating with and without zCAP.
An existing LPAR peaks at 700 MSU running CICS and Db2. You add a new application that draws 200 MSU at the same window. We compare collocating it normally against collocating it under zCAP, reading the MSU the existing middleware is billed on.
| Approach | New app MSU | Counts toward existing peak | Existing middleware billed on |
|---|---|---|---|
| Collocate, no zCAP | 200 | 200 | 900 MSU |
| zCAP, partial attribution | 200 | 100 | 800 MSU |
| zCAP, full attribution | 200 | 0 | 700 MSU |
| Separate dedicated LPAR | 200 | 0 | 700 MSU |
Collocate without zCAP and the existing CICS and Db2 are now billed on 900 MSU, the new application's 200 stacked onto their 700. Under zCAP with full attribution for other middleware, the application's time is removed from the existing peak, so CICS and Db2 stay billed on 700 while the new application is priced on its own footprint. The outcome matches a dedicated LPAR without the cost of standing one up. Attribution is up to 100% for other middleware and up to 50% for z/OS, so the z/OS line sees a partial reduction.
zCAP bites when the eligibility conditions are assumed rather than checked. The application has to be genuinely new, the machine and pricing terms have to qualify, and the zCAP Defining Program and SCRT reporting have to be set up correctly or the attribution does not flow. Get any of those wrong and the new application simply stacks onto the shared peak at full cost. The table maps the conditions to the risk.
| Condition | Why it matters | Risk if missing |
|---|---|---|
| Sub-capacity AWLC, AEWLC, or zNALC | zCAP is built on these sub-capacity terms | No zCAP; application stacks at full capacity |
| Genuinely new application | zCAP is for new workload, not existing rehosting | Disqualification if challenged at audit |
| Eligible machine generation | zCAP requires a qualifying server | Terms unavailable on older hardware |
| zCAP Defining Program in place | The middleware that lets SCRT attribute the work | Attribution does not flow; no reduction |
| Correct SCRT reporting | The mechanism that records the carve out | Application counts in the shared peak anyway |
zCAP terms, attribution percentages, and eligibility are IBM constructs that have evolved across machine generations and pricing programs. Treat the figures here as the mechanism; verify the current zCAP terms and your machine's eligibility before relying on them in a business case.
zCAP is the production sibling of the collocation idea behind Container Pricing for dev and test: both let work share a machine without sharing a price. It operates on the same R4HA and MSU that drive MLC, and its benefit is shaped by your model capacity rating. Building the eligibility case, configuring the reporting, and pricing the result into a renewal or a new application rollout is the work on mainframe cost optimization.
Audit notice or renewal under 18 months out? We mobilize within 48 hours. Rolling out a new z/OS application? Get the zCAP case built before it stacks onto your shared peak.
z Systems Collocated Application Pricing (zCAP) is an IBM sub-capacity pricing approach that lets a qualifying new application run in an existing LPAR alongside other work, yet be priced as if it ran in its own dedicated LPAR. It removes a large share of the new application's processor time from the utilization reported for the other middleware on that LPAR, so adding the application does not inflate the bill for everything around it.
zCAP commonly removes up to 100% of the new application's general purpose processor time from the utilization reported for other middleware, and up to 50% for z/OS itself. The practical effect is that the qualifying application is metered on its own footprint rather than piling onto the shared LPAR peak that drives the rest of the software charges, as the worked calculation above shows.
zCAP requires sub-capacity pricing under AWLC, AEWLC, or zNALC terms on an eligible machine, a qualifying new application, and a zCAP Defining Program: the IBM middleware, such as CICS, Db2, IMS, MQ, or WebSphere Application Server, that manages the new application's processing. The defining program and the reporting setup are what let SCRT attribute the application's work separately.
A separate LPAR gives the new application its own pricing boundary but adds operational overhead and may strand capacity. zCAP achieves a similar pricing outcome while the application stays collocated in an existing LPAR, so you avoid the cost and complexity of standing up dedicated capacity. The trade is the eligibility and reporting discipline zCAP requires.