What it is about
The Technical Specification introduces quantitative indicators that can be used to assess designs, compare variants, and validate service level agreements (SLAs). It covers the infrastructure for power supply and distribution and for environmental control, and it can be applied to other infrastructures such as telecommunications cabling.
It specifies the measurement and calculation of the metrics and of the resilience levels and describes in which phases of the design process the indicators apply. IT equipment, cloud services, software, and business applications are not covered; it sets no limit or target values (CLC/TS 50600‑4‑31:2024, Introduction, Clause 1).
Core requirements in our own words
Three categories: dependability, fault tolerance, availability tolerance.
Dependability comprises reliability, availability, and failure rate, each measured (past), calculated from design data (inherent), or determined under real conditions (operational). Fault tolerance counts single and double points of failure (SPoF, DPoF), availability tolerance the points of reduced availability (SPoRA, DPoRA). Clauses 6.2 and 6.3.
Every indicator applies to an operating point.
The operating point (OP), for example a socket outlet or a row of racks, is the location at which power supply and cooling must jointly deliver the service; it is selected on the basis of the risk analysis. When reporting, the operating point and the assumed load must always be stated. Clauses 4.2 and 6.2.2.
Component metrics are the input data.
Mean time between failures (MTBF), mean time to recovery (MTTR), mean time between maintenance (MTBM), and mean down time (MDT) feed into the calculation. Standardized reliability data are preferred and must be compared with your own data during operation. Clauses 6.2.4 and 6.7.2.
The resilience level makes targets comparable.
A normal resilience level (NRL) consists of four figures: permitted points of failure, reporting period, accepted faults, and accepted down time per event; the operational availability follows from these. A reduced resilience level (RRL) should be defined for planned maintenance. Clause 6.6.
The indicators accompany the design process according to EN 50600‑1.
From strategy through objectives, comparison of designs, and approval to factory acceptance testing, commissioning tests with failure simulation, and operation, the Technical Specification states for each phase what has to be decided or confirmed. Clause 5.1.
In operation, everything is documented and recalculated.
The resilience model, operating points with load assumptions, metrics, points of failure, and calculation method must be provided, and the cause and duration of every breach of the resilience level must be recorded. After structural changes, the model and indicators must be reviewed. Clauses 5.2 to 5.6.
From our seminars: two misconceptions
“Five nines tell you how available the data center is.”
From seminar practice: a percentage leaves open whether the permitted downtime occurs in one block or in ten short interruptions, and every interruption costs the IT a restart. In the resilience level, the Technical Specification defines the number of faults and the down time per event separately, related to an operating point (Clause 6.6.1).
“Availability Class 3 is fault-tolerant.”
In projects, we often encounter the assumption that multiple paths for maintenance during operation rule out a failure. The class describes the design; the number of single points of failure and the operational availability are separate indicators, and the examples in the Technical Specification show Availability Class 3 designs with single points of failure (Clause 6.6.2).
Where Part 4‑31 applies in a project
Planning
Model variants as reliability block diagrams and compare them by the number of points of failure and the calculated availability before the design is approved (Clauses 5.1.5, 6.7.3, Annex C).
Service level agreement
Agree on a resilience level instead of a percentage: reporting period, permitted events, and down time per event at the defined operating point, plus a reduced level for maintenance windows (Clauses 5.1.3, 6.6).
Acceptance and operation
Failure simulations during commissioning tests, ongoing documentation of metrics and failure causes, recalculation after modifications (Clauses 5.1.8, 5.1.9, 5.2).
This protects you from an agreement whose percentage nobody can trace back to the installation in the event of a dispute (Clause 6.6.1).
Status and revision
- Current edition
DIN CLC/TS 50600‑4‑31 (VDE V 0801-600-4‑31):2025‑02, German edition of CLC/TS 50600‑4‑31:2024; Technical Specification without a preceding draft.
- International
ISO/IEC TS 22237-31. According to the European foreword, the Technical Specification is based on the 2023 edition but is not identical to it; the second edition has been available since February 2026 (ISO catalog, as of 17 September 2026).
- Revision
no ongoing revision known. Committee CLC/TC 215, national mirror committee DKE/GK 719.
- Last reviewed
CLC/TS 50600‑4‑31
Frequently asked questions
No. A Technical Specification is the result of standardization work that is not yet published as a standard because of reservations about its content or because of the procedure; VDE pre-standards (Vornormen) are not part of the German body of standards (Deutsches Normenwerk), and experience from application is explicitly requested (national foreword of the German edition). Like the standards of the series, it becomes binding through contracts, specifications of works, and criteria catalogs.
A SPoF is an element whose failure causes the entire system at the operating point to fail; a SPoRA is an element whose failure violates the required operational availability without everything failing (Clauses 3.1, 6.4, 6.5).
No, it complements them. The Technical Specification assigns its examples of resilience levels to the Availability Classes, because a single indicator such as availability does not reflect the complexity of an infrastructure (Introduction, Clause 6.6.2).
No single one. The Technical Specification describes reliability block diagrams according to EN 61078 as applicable and names FMECA, fault tree analysis, Markov analysis, and Petri nets; for comparisons, methods and reliability data must be equivalent (Clause 6.7).
No. It applies to the infrastructure of power supply and environmental control and can be applied to telecommunications cabling; IT equipment, cloud services, software, and business applications are excluded (Clause 1).
Seminars
Related seminars
Training path 3/4
DC-21003Data Center Operations – Professional
5 days · In person · Live webinar
Resilience indicators according to ISO/IEC TS 22237-31, Boolean models for series and parallel configurations, and how to build service level agreements on measurable indicators; this saves you an SLA that cannot be verified in operation.
Next date: 16–20 Nov 2026, onlinePrice plus VAT: €6,990Training path 2/4
DC-21002Data Center Design & Implementation
according to EN 50600 and ISO/IEC 22237
5 days · In person · Live webinar
Availability Classes, redundancy concepts, and the design process according to EN 50600‑1, in which the resilience indicators apply.
Next date: 23–27 Nov 2026, onlinePrice plus VAT: €6,990
All prices plus VAT; the price is the same in every format.
- DIN CLC/TS 50600‑4‑31 (VDE V 0801-600-4‑31):2025‑02 (German edition of CLC/TS 50600‑4‑31:2024), national foreword of the German edition and European foreword, Introduction, Clauses 1, 3.1, 4.2, 5.1 to 5.6, 6.2 to 6.7, Annexes A to E
- ISO/IEC TS 22237-31:2026, ISO catalog (as of 17 September 2026)
- DIN EN 50600‑1:2019 (German edition of EN 50600‑1:2019), design process and Availability Classes
- DCE academy seminar practice: Data Center – General Principles (session April 2026), Data Center Design & Implementation (session November 2025), Data Center Operations – Professional (seminar materials March 2026)
Glossary terms
- resilience
- resilience level (normal, reduced)
- operating point (OP)
- Dependability: reliability, availability, failure rate (past, inherent, operational)
- points of failure (SPoF, DPoF)
- points of reduced availability (SPoRA, DPoRA)
- MTBF, MTTR, MTBM, MDT
- reliability block diagram (RBD)
- FMECA
- system success path
- Technical Specification (CLC/TS)
