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01 The Traditional MLC Model on IBM Z
Monthly Licence Charge (MLC) is IBM's longstanding model for licensing core mainframe software: z/OS, Db2, CICS, IMS, and IBM MQ. Under MLC, customers pay a recurring monthly fee based on processing capacity consumed, measured in MSUs (Million Service Units). Rather than a simple per-processor fee, IBM uses sophisticated metrics to determine charges based on actual workload horsepower.
Rolling 4-Hour Average (R4HA)
IBM measures peak usage of each eligible software product within the month. The highest sustained 4-hour average CPU utilisation determines the billable MSU consumption. If your Db2 workload peaks at an R4HA of 500 MSUs one afternoon and that is the month's highest, Db2 charges are based on 500 MSUs for that entire month.
Tiered Pricing
IBM offers volume-based discounts as MSU levels increase. However, a single usage spike can significantly increase the monthly bill. This is a persistent pain point for IT finance teams and creates tension between capacity availability and licensing cost.
Full Capacity vs Sub-Capacity
Originally, MLC charged at full machine capacity regardless of actual usage. IBM's sub-capacity licensing (now the norm) allows billing based on peak utilised capacity rather than installed capacity. This is a critical cost-saving mechanism for every mainframe shop.
02 Sub-Capacity Licensing on IBM Z
Under sub-capacity licensing, organisations report mainframe usage to IBM monthly using the IBM Sub-Capacity Reporting Tool (SCRT). SCRT gathers detailed utilisation data for all LPARs and eligible products, calculates the R4HA for each product, and produces the sub-capacity report that forms the basis for MLC billing.
SCRT compliance is non-negotiable. IBM requires accurate monthly (or at least quarterly) SCRT reports. Failing to run SCRT or misreporting usage can result in IBM reverting to full-capacity charges or other compliance penalties. SCRT is what enables the "pay for what you use" model. Without it, you pay for everything.
The R4HA mechanism means the highest sustained workload levels drive cost. Many organisations respond with careful capacity management: tuning applications, scheduling batch jobs during off-peak hours, and using capping tools to limit peak CPU usage. By capping peaks, you control costs, but the trade-off is potential performance constraints. A bank might cap its online transaction LPAR to a certain MSU limit to avoid budget overruns, even when hardware could handle more throughput.
IBM also created special programs layered on MLC to address specific use cases: Container Pricing for development/test environments, Mobile Workload Pricing for new mobile transactions, and others. These aimed to reduce costs in growth areas without requiring a full pricing model change, but added to overall complexity. By the late 2010s, the unpredictability and management overhead of MLC billing led IBM to propose Tailored Fit Pricing.
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03 Tailored Fit Pricing — Modern Licensing Options
Introduced in 2019, Tailored Fit Pricing (TFP) represents a significant shift from R4HA-based MLC. Rather than charging monthly based on each month's peak, TFP offers arrangements that behave more like cloud subscriptions or all-you-can-use models. The aim: let customers use mainframes more freely rather than architecting workloads around price.
TFP offers two primary models covering the same IBM Z software products that would be under MLC:
Enterprise Consumption Model — Pay-as-You-Go
Usage-based model measuring aggregate MSU consumption over time (hourly/monthly) rather than monthly peaks. IBM collaborates with the client to establish an annual consumption baseline (typically based on previous 12 months), divided into a predictable monthly rate.
Best for: Organisations with highly variable or seasonal workloads. Short-term spikes no longer cause the full month's bill to jump. They contribute to cumulative annual usage instead.
Key benefit: Much less need for artificial capping. Predictable rate per MSU enables reliable cost forecasting.
Enterprise Capacity Model — Fixed-Price
Full-capacity, fixed-price model. Customer agrees on defined physical capacity (MSUs corresponding to machine/LPAR configuration). IBM charges a fixed monthly fee regardless of actual usage. All IBM Z software in the agreement is fully licensed for the environment.
Best for: Organisations with relatively steady workloads or those wanting to aggressively expand mainframe usage without continual renegotiation.
Caution: You pay for headroom whether you use it or not. Size the capacity commitment wisely.
| Factor | Traditional MLC | Enterprise Consumption | Enterprise Capacity |
|---|---|---|---|
| Pricing Basis | Monthly peak R4HA per product | Aggregate MSU consumption (annual baseline) | Fixed fee on defined physical capacity |
| Cost Predictability | Low. Spikes cause monthly fluctuations. | Medium-High. Annual baseline, predictable rate. | High. Fixed monthly cost regardless of usage. |
| Capping Required? | Often necessary to control peaks. | Less necessary. Spikes averaged over time. | Not needed. All capacity pre-paid. |
| Best For | Flat, predictable usage already optimised. | Variable/seasonal workloads needing flexibility. | Steady workloads with growth ambitions. |
| Compliance Complexity | High. Monthly SCRT, R4HA tracking. | Medium. Consumption vs baseline tracking. | Low. Pre-paid capacity, minimal tracking. |
| Growth Incentives | Limited. Growth increases R4HA and costs. | Growth buckets with discounted rates. | New workloads free within capacity. |
TFP Adoption and Considerations
Both TFP models include additional incentives: no-charge or discounted dev/test capacity, "growth buckets" with discounted rates for workload expansion, and removal of disincentives for modernisation on Z. TFP typically requires z14 or newer hardware and recent z/OS versions. Agreements span several years and cover a broad range of MLC software products.
As of 2024-25, TFP has seen strong uptake. Approximately 68% of mainframe shops are running or preparing to run under TFP, showing rapid adoption. However, TFP is not automatically a cost saver in all cases. Organisations with very flat usage patterns may find traditional MLC with sub-capacity already works efficiently. Others have used TFP as negotiation leverage to secure better MLC discounts. Each CIO should model workloads under both MLC and TFP scenarios before committing.
04 Cost Optimisation Strategies for IBM Z Software
Controlling mainframe software costs requires combining technical and contractual strategies. These approaches optimise IBM software expenses without compromising compliance.
Leverage Sub-Capacity and Intelligent Capping
If on traditional MLC, make full use of sub-capacity pricing. Analyse peak workload drivers and use intelligent job scheduling or soft capping tools to mitigate spikes. Stagger batch jobs and heavy report runs so they do not coincide. The goal: reduce unnecessary peaks, not throttle legitimate business transactions.
Optimise Performance to Reduce MSUs
Identify workload inefficiencies. Even small improvements in application performance or data access lower CPU consumption, directly translating to MSU savings. Tactics include tuning Db2 queries, archiving inactive data, using optimised compilers, and leveraging tools to analyse CICS and Db2 CPU utilisation.
Exploit Specialty Processors (zIIP/zAAP)
IBM Z specialty engines like zIIP offload eligible workloads: Db2 analytics, Java, encryption. Work on zIIPs does not count toward MLC MSU consumption. Moving SQL processing, XML parsing, and other workloads to zIIPs saves significantly. The hardware investment often pays for itself via software cost avoidance.
Evaluate Tailored Fit Pricing
Periodically re-evaluate whether MLC or TFP makes sense. If your team spends excessive effort micro-managing usage to control costs, that is a strong signal to consider TFP. Calculate side-by-side: what would your last 12 months cost under Enterprise Consumption? Under Enterprise Capacity?
Use IBM's Cost Management Tools
Use SCRT and Resource Measurement Facility (RMF) reports regularly to spot trends. Stay informed about IBM programs: Application Development and Test Solution, Mobile Workload Pricing, Country Multiplex Pricing. Upgrading to newer hardware or z/OS versions may provide more favourable pricing metrics.
Negotiate and Right-Size Contracts
Do not treat mainframe software billing as fixed. If your footprint is shrinking, engage IBM or an independent licensing consultant to adjust your MLC baseline. Consider an Enterprise Licence Agreement (ELA) for wide-ranging usage. Approach every renewal as an opportunity for better terms.
Retire or Reallocate Unused Software
Audit your environment for software that is installed and billed via MLC but delivering marginal value. Uninstall unneeded products to remove them from billing calculations. Consolidate workloads onto fewer LPARs when possible. Fewer separate peaks can mean a lower combined peak due to economies of scale in a single LPAR or sysplex. Follow IBM's proper procedures for cancelling licence entitlements.
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05 Compliance and Audit Considerations
Optimising cost must be balanced with strict licence compliance. IBM actively audits customers and has formal audit clauses in its contracts. Known audit triggers include: significant drops in annual IBM spending, major infrastructure changes (hardware upgrades), mergers or acquisitions, or time elapsed since the last audit.
Maintain Accurate SCRT Reporting
Submitting SCRT reports on time every month is non-negotiable. Missing a report or submitting inconsistent data is one of the fastest ways to raise flags. IBM can treat failure to report as non-compliance, charging at full capacity. Automate and validate the SCRT process. Cross-check output for anomalies before submission.
Track Entitlements and Deployments
Know exactly what IBM software you are entitled to use (and on which machines) and compare that to what is installed and running. Maintain a centralised inventory of all IBM Z software licences: licence capacity (MSUs or users), sites/LPARs where deployed. Update whenever there are changes.
Conduct Internal Licence Reviews
Do not wait for IBM to audit. Perform your own "DIY audit" at least annually (monthly mini-audits recommended for mainframe licensing). Review SCRT reports, verify no unlicensed software is running, check that licence adjustments were made with capacity upgrades. Analyse SMF data to ensure no surprises.
Watch for Audit Triggers
Prepare in advance for situations that commonly trigger audits: M&A (ensure entitlements are properly transferred), significant spend decreases (verify genuine usage reductions justify the drop), nearing contract end or declining upgrades. Having records in order allows confident responses.
Educate and Enforce Compliance
System programmers should know not to run IBM software trials or enable features in production without proper licensing. Application teams should understand that deploying new mainframe workloads is also a licensing decision. Establish governance where a licensing SME reviews any new installation or capacity change.
Stay Current with IBM Policies
IBM occasionally updates licensing policies, tools, and metrics: new SCRT versions, changed workload definitions (zIIP eligibility, container pricing metrics), new programmes. Keep an eye on IBM announcements and mainframe user groups. Adhering to latest requirements keeps you compliant and may provide new cost-saving opportunities.
06 CIO Recommendations
Assess Your Licensing Model Fit
Regularly review whether traditional MLC or Tailored Fit Pricing (Consumption vs Capacity) is most cost-effective. Analyse workload patterns (peak vs average usage) and run cost models for different scenarios. Make data-driven decisions. Do not stick with the status quo if a better option exists.
Optimise Capacity and Workload Management
Instruct IT operations to actively manage mainframe workload placement and timing. Implement capacity planning tools and weekly MSU usage monitoring. Treat MSUs like a precious resource. Set performance tuning goals to reduce CPU usage of key transactions. Ensure zIIP processors and updated optimisation software are evaluated and used where appropriate.
Strengthen Licence Governance
Establish robust internal processes: require that any changes to hardware, LPAR configurations, or software installations go through a licence compliance review. Maintain documentation of all IBM software contracts and verify usage aligns with entitlements. Consider appointing a dedicated mainframe licence manager or expanding SAM team scope.
Engage Expert Help When Needed
Do not hesitate to leverage independent IBM licensing experts. Firms like Redress Compliance provide unbiased assessment of your licence position and identify optimisation opportunities that IBM might not reveal. Use them especially during contract negotiations or if you receive an audit notice.
Plan for Audits and Mitigate Risks
Assume an IBM audit will happen at some point and prepare accordingly. Conduct regular self-audits of mainframe software usage and proactively address compliance issues. If you detect exposure (SCRT was not run properly, orphan LPAR not accounted for), address it before IBM does. Being honest and proactive internally means you are ready when auditors arrive.
Budget for Mainframe Software Intelligently
Treat software licensing as a strategic budget item. Forecast MSU consumption and costs for the year. Track quarterly. Use show-back or charge-back to internal business units to encourage efficient mainframe resource use. Set aside contingency budget for true-ups or legitimate usage growth.
Stay Informed on Mainframe Licensing Trends
Keep yourself and your team updated on IBM's latest offerings, pricing initiatives, contract term changes, and competitive models from third-party ISVs. Attend mainframe user groups and licensing-focused webinars. By staying current, you can anticipate changes and avoid being caught off guard.
Independent licensing review pays for itself in the IBM mainframe context. The complexity of MLC pricing, TFP modelling, SCRT compliance, and zIIP eligibility rules means even experienced IT teams benefit from an external perspective. Our IBM Licensing Assessment Service provides a comprehensive audit of your mainframe licensing position, identifying optimisation opportunities, compliance risks, and negotiation leverage points that IBM's own team has no incentive to reveal.
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