Overcoming MySQL Error 1021 (ER_DISK_FULL): Effective Strategies for Freeing Disk Space

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When working with MySQL, encountering Error 1021 with the SQLSTATE code HY000 can halt your database operations. This error indicates that the disk is full and MySQL is unable to proceed because it cannot write to the disk. Addressing this issue promptly is critical to resume normal database functionality.

Understanding Error 1021 – SQLSTATE: HY000 (ER_DISK_FULL)

Error 1021 occurs when the disk partition that holds the MySQL data directory runs out of free space. MySQL requires available disk space for its normal operations, including writing to log files, creating temporary tables, and more. When space runs out, MySQL cannot continue to operate properly, resulting in the “Disk full” error message.

Diagnosing the Issue

To diagnose the disk space issue:

  1. Use the df command to check the available disk space on your server:
df -h
  1. Identify the partitions that are full or nearly full.
  2. Check the size of the MySQL data directory and temporary directories:
du -sh /path/to/mysql/data/dir
du -sh /tmp

Replace /path/to/mysql/data/dir with the actual path to your MySQL data directory.

Fixing the Error

Example 1: Freeing Up Disk Space

You can free up disk space by deleting unnecessary files or moving them to another partition. For example, to clear the /tmp directory safely:

sudo rm -rf /tmp/*

Ensure that no critical processes are using /tmp before clearing it.

Example 2: Increasing Disk Space

If possible, add more disk space to the partition. This could involve resizing partitions, adding a new disk, or increasing the size of a virtual disk if you’re using a virtualized environment.

Example 3: Configuring MySQL to Use a Different Disk

If you have another disk or partition with more space, you can configure MySQL to use it for its data directory or temporary files:

  1. Stop the MySQL server:
sudo service mysql stop
  1. Copy the MySQL data directory to the new location:
sudo cp -R /path/to/mysql/data/dir /new/path/to/data/dir
  1. Update the datadir and tmpdir settings in your my.cnf (or my.ini on Windows) MySQL configuration file to point to the new locations.
  2. Restart the MySQL server:
sudo service mysql start

Example 4: Cleaning Up Binary Logs

If you have binary logging enabled and do not need the old logs, you can purge them:

PURGE BINARY LOGS TO 'mysql-bin.010';

Replace 'mysql-bin.010' with the name of the last binary log file you want to keep.

Example 5: Archiving Old Data

If your databases contain historical data that is not frequently accessed, consider archiving it to free up space.

Example 6: Optimizing Tables

Over time, tables can become fragmented, especially with frequent updates and deletes. Optimize tables to potentially free up space:

OPTIMIZE TABLE table_name;

Replace table_name with the name of the table you want to optimize.

Conclusion

Resolving MySQL Error 1021 requires prompt action to free up or increase disk space. By following the examples provided, you can diagnose the cause of the error and apply the appropriate solution to get your database back up and running. Regular monitoring of disk usage can help prevent this error from occurring in the future. If you find yourself frequently running into disk space issues, consider implementing a more robust storage management strategy.

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