MySQL and MariaDB Disk Temp Tables Per Second Alert

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Use the Disk Temp Tables Per Second alert in Mini DBA to monitor MySQL and MariaDB instances and make this condition visible before it becomes a wider database incident.

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Alert Summary

Platform: MySQL and MariaDB
Alert category: Query
Default enabled: false
Default evaluation frequency: Minute
Threshold label: Disk temp tables/sec
Unit: tables/sec

What Mini DBA Checks

Mini DBA describes this alert as: MySQL is creating temporary tables on disk. Disk-based temp tables are much slower than memory temp tables and often point to large sorts, grouping, or insufficient temp table memory settings. The default evaluation frequency is Minute, so the alert is intended to be close enough to operational reality for live triage. Because duration is used, Mini DBA can avoid treating a single short spike as a full incident when the condition clears quickly.

Why This Alert Is Helpful

This alert protects storage and recovery capacity. It helps you find growth, retention, and backup conditions that can stop writes, break recovery objectives, or leave the server without enough working space for normal database activity.

When To Enable It

Enable it once the instance has a normal workload baseline. It is especially useful on busy OLTP, reporting, and integration systems where resource pressure can quickly become user-visible.

Threshold Guidance

Threshold meaning: Disk temp tables/sec. Major threshold: 10 tables/sec. Minor threshold: 2 tables/sec. Comparison direction: "over". Duration is used, so prefer requiring the condition to persist before paging people for transient spikes. Use higher thresholds on batch-heavy, development, or intentionally bursty systems where brief pressure is expected. Use lower thresholds on latency-sensitive production systems, small instances with little headroom, and services with strict recovery or availability commitments.

Remediation For An Active Alert

Open the related Mini DBA page for the instance, compare the current value with the recent baseline, identify whether the change is caused by workload, configuration, host capacity, or maintenance, then record the corrective action in the incident notes.

Investigation Workflow

Confirm the alert is still active and note the first seen time, affected instance, and severity.
Review the affected disk, tablespace, log stream, backup job, retention setting, and recent growth pattern in Mini DBA before changing configuration or ending sessions.
Compare the current value with the normal baseline for the same time of day or maintenance window.
Record the cause, corrective action, and whether thresholds or routing should be adjusted after the incident.

Avoiding Alert Noise

Storage alerts should usually stay enabled even on quiet systems because the impact of missing them is high. Tune warning thresholds to leave enough time for approval, provisioning, and validation, especially when storage changes are handled by another infrastructure team.