Section 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.
Key Concepts in MLC Licensing
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. This mechanism rewards efficiency over time but penalizes unexpected workload spikes. A single weekend batch job running at peak capacity can shift your entire monthly bill upward.
Tiered Pricing: IBM offers volume-based discounts as MSU levels increase. However, a single usage spike can significantly increase the monthly bill. Many CIOs find that the tiered structure creates unpredictable monthly bills and incentivises cost avoidance through artificial capacity constraints rather than infrastructure optimisation.
Full Capacity vs Sub-Capacity: Originally, MLC charged at full machine capacity. IBM's sub-capacity licensing allows billing based on peak utilised capacity rather than installed capacity. This distinction is critical: organisations with modest utilisation can achieve significant cost reduction by moving to sub-capacity reporting.
The Classic MLC Challenge: IT teams often 'architect around price,' holding back on utilising available capacity due to cost concerns. This creates underutilised infrastructure and leaves performance optimisation opportunities on the table. Independent review frequently reveals that the TCO of improved performance outweighs the licensing cost increase.
Section 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. SCRT compliance is non-negotiable: IBM requires accurate monthly reports. Failing to run SCRT can result in IBM reverting to full-capacity charges, which can increase your monthly bill by 300-500% depending on actual utilisation.
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 constrain peak resource consumption. These tactics work but create operational overhead and constrain infrastructure flexibility.
IBM advisory specialists validate SCRT configurations, identify reporting gaps, and ensure your sub-capacity position is audit-ready. Common SCRT issues include:
- Misclassification of LPARs as eligible or non-eligible for reportable capacity
- Incorrect software product mapping across infrastructure
- Configuration drift: infrastructure changes not reflected in SCRT settings
- Audit trigger events: evidence that your SCRT data contradicts actual infrastructure deployment
Need Help Optimising Sub-Capacity Reporting?
Section 03: Tailored Fit Pricing
Introduced in 2019, TFP offers two primary models designed to address MLC predictability challenges:
Enterprise Consumption Model (Pay-as-You-Go)
Usage-based billing with aggregate MSU consumption measured over an extended period rather than monthly peaks. This model rewards sustained efficiency but removes the monthly peak penalty. Organisations with variable workloads or growth trajectories often see cost stability and predictability improve significantly under ECM.
Enterprise Capacity Model (Fixed-Price)
Full-capacity fixed monthly fee regardless of actual utilisation. This model suits organisations with stable, well-understood workloads. It eliminates reporting compliance overhead and removes all usage-based billing uncertainty. The trade-off: you pay for full capacity even if actual utilisation is 40-50%.
Comparative Analysis: Traditional MLC vs TFP Models
Traditional MLC incentivises cost avoidance through architectural constraints. TFP models incentivise either sustained efficiency (ECM) or predictable budgeting (ECM). As of 2024-25, TFP has seen strong uptake: approximately 68% of mainframe shops are running or preparing to run under TFP.
Optimise Your Baseline Before Committing to TFP: CIOs commonly negotiate TFP agreements based on historical MLC spend. But historical spend reflects years of cost-avoidance architecture and sub-optimal performance. Redress recommends conducting a cost assessment to establish your actual cost position before TFP negotiation. Baseline optimisation often reveals 15-25% cost reduction opportunities that become embedded in your TFP pricing.
Section 04: Cost Optimisation Strategies
Seven proven strategies for controlling mainframe software costs:
1. Leverage Sub-Capacity Licensing
If you are on traditional MLC and not using sub-capacity reporting, SCRT compliance is your first priority. This single change often reduces costs by 20-40% depending on your utilisation profile.
2. Optimise Performance and Resource Utilisation
Tuning applications to run more efficiently within existing infrastructure reduces peak MSU consumption. Database query optimisation, batch job scheduling, and workload balancing across LPARs all contribute. The challenge: performance tuning requires expertise and sustained effort.
3. Exploit Specialty Processors
IBM Z specialty processors (zIIP for Java/XML, zAAP for application-level computation) have separate licensing from base software. Offloading eligible workloads to specialty processors reduces base software MSU consumption. Many organisations leave 10-20% of eligible workload on general processors due to application configuration or architectural choices.
4. Evaluate Tailored Fit Pricing
If you have predictable or slowly-growing workloads, ECM or ECF models often cost less than traditional MLC. If you have highly variable workloads, the break-even analysis is more complex.
5. Use IBM's Cost Management Tools
IBM publishes cost estimation and capacity planning tools. Organisations that use these tools actively tend to avoid surprise billing and cost creep.
6. Negotiate and Right-Size Contracts
IBM licensing terms are negotiable. Benchmark data from industry peers provides leverage for renegotiation. Independent advisors have visibility into typical pricing across industries and organisation sizes.
7. Retire Unused Software
Many organisations licence software products that are no longer actively used. IBM charges for all licenced products regardless of active usage. Regular audits of installed software often identify retirement opportunities worth 5-15% cost reduction.
Oracle Licensing Insights — Stay Informed
Section 05: Compliance and Audit Considerations
Six critical areas for maintaining a defensible mainframe licensing position:
Maintain Accurate SCRT Reporting
Monthly SCRT execution and accurate data submission are your foundation for audit defence. Any gaps or inconsistencies in SCRT data are audit triggers. Organisations that cannot produce consistent SCRT execution logs risk IBM challenging the validity of their reported MSU position.
Track Entitlements
Document every licence purchase, entitlement change, and software retirement. Many audit disputes arise from unclear entitlement positions. A CIO cannot credibly defend against IBM audit claims without documented proof of what you licensed when.
Conduct Internal Reviews
Regular internal audits of your SCRT configuration, infrastructure mapping, and licence documentation identify gaps before IBM audit does. Proactive internal review is substantially less costly than reactive remediation after IBM initiates contact.
Watch for Audit Triggers
Certain activities heighten IBM audit risk: infrastructure changes without corresponding SCRT updates, significant SCRT data variations month-to-month, or evidence of capacity constraints that contradict your reported utilisation profile.
Educate and Enforce Compliance
SCRT compliance requires disciplined execution. Monthly SCRT runs must be a scheduled, monitored process. Infrastructure changes must trigger SCRT configuration reviews. Organisations that treat SCRT compliance as a one-time setup rather than an ongoing process create audit exposure.
Stay Current with IBM Policy Changes
IBM changes its licensing policies and SCRT requirements periodically. Staying informed about policy updates prevents unintended compliance violations and identifies new cost optimisation opportunities.
Engage Independent Experts for Audit Defence: When IBM initiates audit, the dynamics shift dramatically. IBM has access to your infrastructure, SCRT data, and entitlements. Independent experts can help you understand your actual compliance position, identify defensible positions, and negotiate settlements that reflect actual licensing exposure rather than IBM's initial audit claims.
Section 06: CIO Recommendations
1. Assess Your Licensing Model
Are you on traditional MLC, or have you moved to TFP? If traditional MLC, is sub-capacity reporting active and accurate? Compare your current cost model to TFP pricing. The cost differential may justify model transition.
2. Establish Capacity Management Discipline
Implement a formal process for SCRT execution, infrastructure change notification, and quarterly compliance review. Capacity management discipline pays dividends in both cost control and audit defence.
3. Establish Licence Governance
Designate a single function responsible for all IBM mainframe licensing decisions. This prevents duplicate licence purchases, ensures consistent SCRT configuration, and maintains a single authoritative view of your entitlements and compliance position.
4. Engage Independent Advisory When Needed
Independent IBM licensing advisors bring benchmark data, technical expertise in cost optimisation, and defensible positions in audit negotiations. Consider advisory engagement as part of your annual licensing review cycle.
5. Prepare for Audit Defence
Proactive audit preparation costs less and yields better outcomes than reactive audit response. Document your compliance position, SCRT configuration, and entitlements before IBM initiates contact.
6. Budget for Realistic Costs
Many CIOs under-budget mainframe software costs based on historical spend. Historical spend reflects artificial capacity constraints, not your actual cost baseline. Build more realistic budgets based on your infrastructure's true capacity and utilisation profile.
7. Stay Informed
IBM releases new licensing models, tools, and policy changes regularly. CIOs who stay informed about mainframe licensing trends have better information for strategic decisions and can identify cost optimisation opportunities earlier than peers.