When the database volume has no free blocks, MySQL may reject inserts/updates, fail temporary tables or stop. WordPress can still serve cached pages while saves, logins, cron and forms fail.
Stop non-essential writes and backups immediately. Deleting unknown database files is dangerous; InnoDB data and logs are not disposable cache.
Confirm which filesystem is full
Inspect the MySQL data, temporary, log and backup filesystems plus inode usage. A root volume with space does not help if /var/lib/mysql or a hosting quota is full.
Record:
filesystem/quota
free bytes and inodes
largest directories
MySQL error timestamp
recent backup/import/log growthOn managed hosting, request provider evidence instead of unsupported server commands.
Contain write activity
Pause imports, backups, scans, email queues and bulk edits through their supported controls. Consider a maintenance mode that prevents new writes while keeping a clear public message.
Do not repeatedly restart MySQL or submit WordPress forms. Failed writes can create partial operations and more logs.
Preserve administrator/SSH access before changing services.
Identify recoverable space
Find old local backups, temporary archives, cache files and rotated logs that have an approved retention policy. Move important backups off-server before deleting.
Never delete active MySQL files such as ibdata, redo/undo logs, binary logs or table files manually. Binary-log purging must respect replication and point-in-time recovery.
Use the host/database administrator for engine-managed cleanup.
Allow for temporary database space
MySQL needs space beyond the final table size for sorting, temporary tables, index rebuilds, crash recovery and binary logs. Leaving only a few megabytes after emergency cleanup can make the next ordinary query fail.
Measure the largest expected import, backup and ALTER TABLE, then establish a higher operational threshold. If the hosting quota cannot provide that headroom, expand or migrate storage before maintenance. Do not start table optimisation merely to reclaim space; it may temporarily require another copy of the table.
Check database and binary logs
An error loop can grow MySQL, PHP or web logs quickly. Preserve a bounded incident excerpt, then rotate/truncate only through supported logging controls.
Binary logs may dominate after imports. Confirm replication positions and backup policy before an authorised purge.
Do not disable all logging permanently; the recurrence would become invisible.
Restore service cautiously
Once safe headroom exists, start or recover MySQL through the panel/service manager and read its error log. InnoDB crash recovery may require additional temporary space.
Do not open public writes until recovery completes. Confirm WordPress connects and read-only queries work first.
If corruption appears, take snapshots/backups and follow engine-aware repair rather than generic table operations.
Find the growth source
Measure table and directory sizes. Common causes include scheduled-action logs, sessions, security logs, revisions, cache tables, failed imports and local backup accumulation.
Restore supported cleanup schedules and fix cron. Do not remove orders, submissions or audit history based only on table size.
Bot traffic can create sessions/logs; rate-limit abusive paths narrowly.
Plan durable capacity
Set alerts well before zero space and reserve headroom for temporary tables, upgrades and restores. Keep database and backups on appropriately planned storage.
Retention should specify what is kept, where and for how long. An off-server backup protects against a database disk that fails entirely.
Estimate growth during campaigns/imports, not only normal days.
Verify writes and integrity
After recovery, save a controlled draft/option, run scheduled tasks and inspect MySQL/PHP logs. Test backup creation to external storage and a sample restore.
Monitor free space through several write cycles. Recurring care should alert on bytes, inodes and abnormal growth; recovery is complete when WordPress writes reliably and the disk has sustainable headroom.