XAMPP - MySQL shutdown unexpectedly

Question

When I open XAMPP and click start MySQL button and it gives me an error. I had started it just before, but now it isn't working.

12:19:12 PM [mysql] Attempting to start MySQL app...
12:19:12 PM [mysql] Status change detected: running
12:19:13 PM [mysql] Status change detected: stopped
12:19:13 PM [mysql] Error: MySQL shutdown unexpectedly.
12:19:13 PM [mysql] This may be due to a blocked port, missing dependencies,
12:19:13 PM [mysql] improper privileges, a crash, or a shutdown by another method
12:19:13 PM [mysql] Press the Logs button to view error logs and check
12:19:13 PM [mysql] the Windows Event Viewer for more clues
12:19:13 PM [mysql] If you need more help, copy and post this
12:19:13 PM [mysql] entire log window on the forums

Here is the contents of the error log:

2013-08-02 12:19:12 4536 [Note] Plugin 'FEDERATED' is disabled.
2013-08-02 12:19:12 f64 InnoDB: Warning: Using innodb_additional_mem_pool_size is DEPRECATED. This option may be removed in future releases, together with the option innodb_use_sys_malloc and with the InnoDB's internal memory allocator.
2013-08-02 12:19:12 4536 [Note] InnoDB: The InnoDB memory heap is disabled
2013-08-02 12:19:12 4536 [Note] InnoDB: Mutexes and rw_locks use Windows interlocked functions
2013-08-02 12:19:12 4536 [Note] InnoDB: Compressed tables use zlib 1.2.3
2013-08-02 12:19:12 4536 [Note] InnoDB: Not using CPU crc32 instructions
2013-08-02 12:19:12 4536 [Note] InnoDB: Initializing buffer pool, size = 16.0M
2013-08-02 12:19:12 4536 [Note] InnoDB: Completed initialization of buffer pool
2013-08-02 12:19:12 4536 [Note] InnoDB: Highest supported file format is Barracuda.
2013-08-02 12:19:12 4536 [Note] InnoDB: The log sequence numbers 0 and 0 in ibdata files do not match the log sequence number 1616798 in the ib_logfiles!
2013-08-02 12:19:12 4536 [Note] InnoDB: Database was not shutdown normally!
2013-08-02 12:19:12 4536 [Note] InnoDB: Starting crash recovery.
2013-08-02 12:19:12 4536 [Note] InnoDB: Reading tablespace information from the .ibd files...

The most important error message is here:

2013-08-02 12:19:12 4536 [ERROR] InnoDB:
Attempted to open a previously opened tablespace.
Previous tablespace mysql/innodb_table_stats uses space ID: 1 at filepath: .\mysql\innodb_table_stats.ibd.
Cannot open tablespace xat/payments which uses space ID: 1 at filepath: .\xat\payments.ibd

The rest of the log:

InnoDB: Error: could not open single-table tablespace file .\xat\payments.ibd
InnoDB: We do not continue the crash recovery, because the table may become
InnoDB: corrupt if we cannot apply the log records in the InnoDB log to it.
InnoDB: To fix the problem and start mysqld:
InnoDB: 1) If there is a permission problem in the file and mysqld cannot
InnoDB: open the file, you should modify the permissions.
InnoDB: 2) If the table is not needed, or you can restore it from a backup,
InnoDB: then you can remove the .ibd file, and InnoDB will do a normal
InnoDB: crash recovery and ignore that table.
InnoDB: 3) If the file system or the disk is broken, and you cannot remove
InnoDB: the .ibd file, you can set innodb_force_recovery > 0 in my.cnf
InnoDB: and force InnoDB to continue crash recovery here.

What is the cause of these errors and how can I rectify them?

Answer 1

Stop there! Please do NOT delete ibdata1 file!

Deleting this file is like playing a Russian roulette with your databases, it could work and restablish everything, but also, probably could harm every database you have. Instead, first try using the MySQL backup folder which is included with XAMPP. So do the next:

1. Rename the folder mysql/data to mysql/data_old (you can use any name)
2. Create a new folder mysql/data
3. Copy the content that resides in mysql/backup to the new mysql/data folder
4. Copy all your database folders that are in mysql/data_old to mysql/data (skipping the mysql, performance_schema, and phpmyadmin folders from data_old)
5. Finally copy the ibdata1 file from mysql/data_old and replace it inside mysql/data folder
6. Start MySQL from XAMPP control panel

And, voilà!