What does 99.9% uptime actually allow?

Over a 30-day month, 99.9% availability permits roughly 43 minutes of downtime. The allowance matters less than the definition of unavailable and the list of exclusions, since scheduled maintenance and third-party dependencies are commonly carved out of the measurement.

Are service credits worth negotiating?

They are usually capped at a portion of the monthly fee for the affected service and designated as the sole remedy for the failure, so they rarely approach the cost of an outage. A termination right for repeated or sustained failures generally provides more leverage than a larger credit percentage.

Which SLA matters more day to day?

The support SLA, for most enterprise software. Availability credits are claimed rarely, while response times, severity assignment, coverage hours, and escalation paths are exercised whenever something goes wrong — including the many incidents that never meet the contractual definition of downtime.

Uptime SLA vs Support SLA: Buyers Negotiate One and Enforce the Other

Comparison · enterprise · 5 min read · last verified 2026-07-21

Reviewed before publication Editorial board Independent commercial review

In shortAn uptime SLA commits to availability and defines a credit when it is missed; a support SLA commits to response times for reported issues. The second one governs daily operations.

An uptime SLA commits a vendor to a stated level of service availability and defines the remedy when that level is missed; a support SLA commits the vendor to response — and sometimes resolution — timeframes for issues raised through support channels.

Uptime SLA vs support SLA at a glance

What is promised. Availability of the service versus responsiveness of the vendor's people.
How it is measured. Uptime is measured by the vendor's monitoring against a defined scope. Support is measured from ticket timestamps against severity definitions.
What the remedy is. Uptime failures typically produce a service credit. Support failures often carry no automatic remedy at all.
How often it is invoked. Availability credits are claimed rarely. Support commitments are exercised continuously.
Who feels it. Uptime failures are visible to everyone at once. Support failures are felt by the specific team blocked on an unanswered ticket.
What it is worth negotiating for. A higher availability percentage changes little in practice. Severity definitions, coverage hours, and escalation paths change daily working life.

What an uptime SLA is

An uptime SLA states a target availability over a measurement period, usually a calendar month, and defines what happens if the vendor misses it. The percentages translate to concrete allowances over a 30-day month: 99.5% permits about 3.6 hours of downtime, 99.9% permits roughly 43 minutes, and 99.99% permits about four minutes.

The percentage is the least interesting part of the clause. What determines whether the commitment means anything:

Scope. Which components are covered. APIs, the web application, background jobs, and integrations are often treated differently, and a service can be technically available while the part a customer depends on is not.
The definition of unavailable. Total failure, error rate above a threshold, or severe degradation. Degradation is where most real incidents live and where many definitions are silent.
Exclusions. Scheduled maintenance, emergency maintenance, customer-caused issues, third-party dependencies, and beta features are commonly excluded. Broad exclusions can consume the commitment entirely.
Measurement authority. Whether the vendor's monitoring is definitive, and whether measurement is aggregated globally or evaluated per region.
The remedy mechanics. Credits are usually a percentage of the monthly fee for the affected service, capped, claimable only on written request within a stated window, and designated as the sole and exclusive remedy for the failure.

That last point is the one buyers most often miss. A credit is a partial refund of a monthly fee for a service that was unavailable — it does not compensate for the cost of the outage, and the requirement to claim it within a window means many earned credits are never taken.

What a support SLA is

A support SLA governs the vendor's responsiveness to reported problems. Its structure is different in kind:

Severity definitions. Usually a tiered scheme from total production outage down to cosmetic issues and questions. Who assigns severity — and whether the vendor can unilaterally downgrade it — is the clause worth reading twice.
Response versus resolution. Most agreements commit to a first response time. Resolution commitments are rarer, and where they exist they are usually framed as continuous effort rather than a deadline, because resolution time depends on the defect.
Coverage. Business hours in which time zone, holidays, and whether the highest severity tier carries around-the-clock coverage.
Channels and named contacts. Whether a portal ticket, an email, or a phone call starts the clock, and how many of the customer's people may open a case.
Escalation. A defined path with named roles and elapsed-time triggers. This is the most useful part of a support SLA and the part most frequently absent.

How they relate

Both appear in the same agreement and are often bundled with pricing tiers, but they answer different questions. The uptime SLA answers "what do we owe you when the service fails." The support SLA answers "how fast do we engage when something goes wrong."

They interact in one important way: an incident that does not meet the contractual definition of unavailable still needs someone to work it. Degradation, data quality problems, integration failures, and misconfigurations produce no credits and consume most of the operational pain. Those are governed entirely by the support commitments.

Both also sit inside the broader risk allocation of the master service agreement, where limitation of liability, termination rights, and the sole-remedy language determine what the service levels are actually worth. Reading service levels without reading those clauses gives a distorted picture.

Which to use when

Prioritize the uptime SLA when the service is in a real-time transaction path, when a defined outage has immediate downstream cost, or when internal governance requires a documented availability commitment for a vendor of record. Even then, negotiate the definition of unavailable and the exclusions before negotiating the percentage — a 99.99% commitment with generous exclusions is weaker than 99.9% measured strictly.

Prioritize the support SLA when the service is operationally central but not second-by-second critical, which describes most enterprise software. The commitments that change outcomes are severity assignment rights, coverage hours aligned to the team's working day, a named escalation contact, and a first-response time for the top severity tier that is short enough to matter.

Prioritize the termination right in both cases. A right to exit without penalty after repeated or sustained failures is usually worth more than any credit schedule, because it is the only remedy proportional to the harm.

Two practical notes. First, service levels are commitments someone has to operate against after signature, which is why they belong in the scope discussed while an implementation plan is agreed before signature rather than being handled as a late contract exhibit. Second, when a portfolio is being reviewed under vendor consolidation pressure, inconsistent support tiers across similar vendors are a common finding — and the cheapest fix is usually aligning severity definitions and escalation paths rather than buying a higher availability number nobody will ever claim against.