SLA vs OLA vs SLO: the differences
These acronyms are used loosely, which makes contracts and reports confusing. In short: an SLA is a promise to a customer, an OLA is a promise between your own teams, and an SLO is a measurable target inside either.
SLA: service level agreement
An agreement between a service provider and its customer about the level of service. It states what is delivered, how it is measured and what happens if it is missed, for example service credits. Example: “P1 tickets get a first response within 30 minutes during business hours.”
OLA: operational level agreement
An agreement between internal teams that support the SLA. The customer never sees it. Example: the network team agrees to answer a P1 escalation from the service desk within 15 minutes, so the service desk can keep its 30-minute promise.
UC: underpinning contract
The same idea with an outside supplier. If your SLA depends on an ISP or a hardware vendor, the contract with them needs to be at least as strong as what you promise your customer.
SLO: service level objective
A specific, measurable target, such as “respond to 95% of P1 tickets within 30 minutes”. An SLA is made of one or more SLOs. Teams also set stricter internal SLOs than the ones in the contract, to leave a safety margin.
SLI: service level indicator
The measurement itself: the actual percentage of P1 tickets answered within 30 minutes this month. You compare the SLI with the SLO to know whether you are on target.
How they fit together
| Term | Between | Answers |
|---|---|---|
| SLA | Provider and customer | What do we promise? |
| OLA | Internal teams | What do we need from each other? |
| UC | Provider and supplier | What do we need from suppliers? |
| SLO | Inside an agreement | What is the target? |
| SLI | Measurement | How are we doing? |
What this means for IT support
Most small IT support providers need only an SLA with each client and a clear way to measure it. Start by calculating compliance correctly, then show it in a client SLA report.