17.20 InnoDB Troubleshooting

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MySQL 8.4 Reference Manual Including MySQL NDB Cluster 8.4

17.20 InnoDB Troubleshooting

The following general guidelines apply to troubleshooting InnoDB problems:

• When an operation fails or you suspect a bug, look at the MySQL server error log (see Section 7.4.2, “The Error Log”). Server Error Message Reference provides troubleshooting information for some of the common InnoDB-specific errors that you may encounter.
• If the failure is related to a deadlock, run with the innodb_print_all_deadlocks option enabled so that details about each deadlock are printed to the MySQL server error log. For information about deadlocks, see Section 17.7.5, “Deadlocks in InnoDB”.
• If the issue is related to the InnoDB data dictionary, see Section 17.20.4, “Troubleshooting InnoDB Data Dictionary Operations”.
• When troubleshooting, it is usually best to run the MySQL server from the command prompt, rather than through mysqld_safe or as a Windows service. You can then see what mysqld prints to the console, and so have a better grasp of what is going on. On Windows, start mysqld with the --console option to direct the output to the console window.
• Enable the InnoDB Monitors to obtain information about a problem (see Section 17.17, “InnoDB Monitors”). If the problem is performance-related, or your server appears to be hung, you should enable the standard Monitor to print information about the internal state of InnoDB. If the problem is with locks, enable the Lock Monitor. If the problem is with table creation, tablespaces, or data dictionary operations, refer to the InnoDB Information Schema system tables to examine contents of the InnoDB internal data dictionary.

InnoDB temporarily enables standard InnoDB Monitor output under the following conditions:

• A long semaphore wait
• InnoDB cannot find free blocks in the buffer pool
• Over 67% of the buffer pool is occupied by lock heaps or the adaptive hash index
• If you suspect that a table is corrupt, run CHECK TABLE on that table.