--- title: "Status Page & Incident Management Glossary" description: "Plain-English definitions of status page and incident terms: SLA, SLO, SLI, uptime, MTTR, MTTD, incident stages, partial vs major outage, postmortem and more." url: https://statusentry.com/glossary updated: 2026-10-20 --- Glossary # Status page & incident glossary Plain-English definitions of the terms you'll meet when running a status page and handling incidents. [Status page](https://statusentry.com/glossary#status-page) · [Component](https://statusentry.com/glossary#component) · [Incident](https://statusentry.com/glossary#incident) · [Incident update](https://statusentry.com/glossary#incident-update) · [Scheduled maintenance](https://statusentry.com/glossary#scheduled-maintenance) · [Maintenance window](https://statusentry.com/glossary#maintenance-window) · [Operational](https://statusentry.com/glossary#operational) · [Degraded performance](https://statusentry.com/glossary#degraded-performance) · [Partial outage](https://statusentry.com/glossary#partial-outage) · [Major outage](https://statusentry.com/glossary#major-outage) · [Uptime](https://statusentry.com/glossary#uptime) · [Downtime](https://statusentry.com/glossary#downtime) · [SLA](https://statusentry.com/glossary#sla-service-level-agreement) · [SLO](https://statusentry.com/glossary#slo-service-level-objective) · [SLI](https://statusentry.com/glossary#sli-service-level-indicator) · [Error budget](https://statusentry.com/glossary#error-budget) · [MTTD](https://statusentry.com/glossary#mttd-mean-time-to-detect) · [MTTA](https://statusentry.com/glossary#mtta-mean-time-to-acknowledge) · [MTTR](https://statusentry.com/glossary#mttr-mean-time-to-resolve) · [MTBF](https://statusentry.com/glossary#mtbf-mean-time-between-failures) · [Incident severity](https://statusentry.com/glossary#incident-severity) · [Postmortem](https://statusentry.com/glossary#postmortem) · [Root cause analysis](https://statusentry.com/glossary#root-cause-analysis-rca) · [Subscriber](https://statusentry.com/glossary#subscriber) · [Endpoint monitoring](https://statusentry.com/glossary#endpoint-monitoring) · [Private status page](https://statusentry.com/glossary#private-status-page) · [Status badge](https://statusentry.com/glossary#status-badge) ## Status page A public or private web page that shows the current health of a product's services, lists active incidents and scheduled maintenance, and lets people subscribe to updates. [Create a free status page](https://statusentry.com/free-status-page). ## Component One part of your product shown on a status page, such as Website, API or Payments. Each component has its own status and uptime history. Statusentry calls these services. ## Incident An unplanned event that disrupts or degrades a service. On a status page it moves through Investigating, Identified, Monitoring and Resolved. [Incident communication templates](https://statusentry.com/blog/incident-communication-templates). ## Incident update A timestamped message posted to an incident explaining what's affected, what you're doing and when the next update will come. [Incident update generator](https://statusentry.com/tools/incident-update-generator). ## Scheduled maintenance Planned work announced in advance, with a start and end time and the expected impact on users. [Maintenance announcement templates](https://statusentry.com/blog/how-to-announce-scheduled-maintenance). ## Maintenance window The agreed period during which scheduled maintenance happens, often at a low-traffic time and often excluded from SLA calculations. ## Operational The status of a component that is working normally. ## Degraded performance A component works but is slower or less reliable than usual. ## Partial outage A component is unavailable for some users, regions or features, but not all. ## Major outage A component is unavailable for most or all users. ## Uptime The share of time a service is available, usually shown as a percentage over a period such as 30 or 90 days. [Uptime calculator](https://statusentry.com/tools/uptime-calculator). ## Downtime Time during which a service is unavailable to users. ## SLA (service level agreement) A promise to customers about availability or performance, such as 99.9% monthly uptime, often with service credits if it isn't met. [See allowed downtime for any SLA](https://statusentry.com/tools/uptime-calculator). ## SLO (service level objective) An internal reliability target, usually stricter than the SLA, that a team aims to meet. ## SLI (service level indicator) The metric used to measure an SLO, for example the percentage of successful requests. ## Error budget The amount of unreliability an SLO allows. A 99.9% SLO leaves a 0.1% error budget, about 43 minutes a month. ## MTTD (mean time to detect) The average time between a problem starting and the team finding out about it. ## MTTA (mean time to acknowledge) The average time between an alert and someone starting to work on it. ## MTTR (mean time to resolve) The average time from the start of an incident to full recovery. Sometimes used for mean time to repair or recover. ## MTBF (mean time between failures) The average time a system runs between incidents. ## Incident severity A level, such as SEV1 to SEV3, that ranks how serious an incident is and decides who responds and how quickly. ## Postmortem A written review after an incident covering what happened, why, and what will change. Also called a post-incident review. A shorter public version is often published on the status page. [Example public postmortem](https://statusentry.com/blog/postmortems). ## Root cause analysis (RCA) The process of finding the underlying cause of an incident rather than only its symptoms. ## Subscriber Someone who signs up on a status page to receive incident and maintenance notifications by email, Slack, webhook or SMS. ## Endpoint monitoring Automated checks that request a URL at set intervals and alert you when it fails or responds slowly. [Endpoint monitoring guide](https://statusentry.com/blog/endpoint-monitoring). ## Private status page A status page visible only to signed-in users, such as employees or specific customers. [Private status pages in Statusentry](https://statusentry.com/blog/private-status-pages). ## Status badge A small embeddable widget that shows your current status on another site, such as your app or docs. [Status badge and widget](https://statusentry.com/blog/status-embed-badge-widget). More free resources: [tools, templates and pricing guides](https://statusentry.com/resources).