原来自己用的是为了装的， 所以在设置database usage（如下图1）的时候按照discuz官方的建议，选的都是Non-Transactional Database Only（只支持MyISAM数据引擎的非事务数据库），用MyISAM数据库，还没涉及到需要InnoDB，因此打算直接不加载INNODB引擎。后来在做WordPress，一开始还不知道原来WordPress用的是InnoDB数据引擎，于是在原来的数据库里面就建了一个数据库,一开始也没发觉问题，安装，导入sql，都没问题，当时也没多想。直到这几天因为又要装多一个WordPress，用phpmyadmin访问数据库多一点，问题来了。老是一访问WordPress的数据库，就弹出错误提示“Mysqld-nt.exe应用程序错误：“0x005346c4”指令引用的“0x00786000”内存，该内存不能为读...”，然后就MySQL服务也停了，登陆不了，整个数据库都访问不了。

图1 设置数据库类型

纠结了挺久，也忘了是看到什么文章触发了灵感，反正后来才知道原来是数据引擎不同惹的祸。于是就想到重新运行次设置向导，把数据库类型改成支持InnoDB引擎的。马上行动，在向导里设置数据库类型（也就是图1的database usage）那里，设置成第二项，还在后面的InnoDB Tablespace Settings里把InnoDB数据文件设置放在D:\MySQL InnoDB Datafiles目录里。但是在最后execute执行的时候，却老是在Start Service那里出问题，如下图2。

图2 Start service出错

按照网上的某些做法，卸载了MySQL服务，也没重启就重新设置，问题如故；把服务卸载了，重启后再重新设置，则是启动服务成功，但是在后面的Applying Security Settings的时候有新的问题，如下图3。图2那里的错误提示则变成“ERROR 2003: Can't connect to MySQL server on 'localhost' (10061)"， 说明MySQL还是没有启动，或者启动过，出错又关了。

顺便提一下，在MySQL5里（其他版本的我不知道）每运行一次设置向导，只要按了execute执行，都会在MySQL5的安装目录下自动生成一个原来的MySQL的设置文件my.ini的备份bak文件。并且将以修改的时间命名。因此如果设置出了问题，可以从备份文件恢复。

后来还是在错误日志里找到思路。错误日志就是放在 MySQL5安装目录\Data 目录里的那个以你的计算机名命名的.err文件。

首先我找到以下一段：

InnoDB: Error: log file .\ib_logfile0 is of different size 0 52428800 bytes

InnoDB: than specified in the .cnf file 0 10485760 bytes!

101001  9:47:42 [ERROR] Default storage engine (InnoDB) is not available

101001  9:47:42 [ERROR] Aborting

101001  9:47:42 [Note] D:\MySQL5\bin\mysqld-nt: Shutdown complete

于是就到“MySQL5安装目录\Data ”目录里把ib_logfile0日志文件删掉，重启MySQL服务，还是提示10067错误。再去查看err文件。

101001 18:39:29  InnoDB: Log file .\ib_logfile0 did not exist: new to be created

InnoDB: Setting log file .\ib_logfile0 size to 109 MB

InnoDB: Database physically writes the file full: wait...

InnoDB: Progress in MB: 100

InnoDB: Error: log file .\ib_logfile1 is of different size 0 52428800 bytes

InnoDB: than specified in the .cnf file 0 114294784 bytes!

101001 18:39:30 [ERROR] Default storage engine (InnoDB) is not available

101001 18:39:30 [ERROR] Aborting

101001 18:39:30 [Note] D:\MySQL5\bin\mysqld-nt: Shutdown complete

可以看到，ib_logfile0的问题解决了，但是同样的问题却出在ib_logfile1上面了。于是依样画葫芦，把ib_logfile1删了，再重启MySQL服务，却发现没用。难道是还要重启系统。果真，把前面两个ib_logfile删了，重启系统就搞定了。前面的可能是因为刚开机，所以也行。实际上是需要重启系统的。这时的日志如下

101001 19:19:24  InnoDB: Log file .\ib_logfile0 did not exist: new to be created

InnoDB: Setting log file .\ib_logfile0 size to 109 MB

InnoDB: Database physically writes the file full: wait...

InnoDB: Progress in MB: 100

101001 19:19:26  InnoDB: Log file .\ib_logfile1 did not exist: new to be created

InnoDB: Setting log file .\ib_logfile1 size to 109 MB

InnoDB: Database physically writes the file full: wait...

InnoDB: Progress in MB: 100

InnoDB: Cannot initialize created log files because

InnoDB: data files are corrupt, or new data files were

InnoDB: created when the database was started previous

InnoDB: time but the database was not shut down

InnoDB: normally after that.

101001 19:19:27 [ERROR] Default storage engine (InnoDB) is not available

101001 19:19:27 [ERROR] Aborting

101001 19:19:27 [Note] D:\MySQL5\bin\mysqld-nt: Shutdown complete

好了，现在只剩下最后一个问题了Default storage engine (InnoDB) is not available。去services.msc里面启动MySQL服务，还是出错。但是日志却是显示

InnoDB: No valid checkpoint found.

InnoDB: If this error appears when you are creating an InnoDB database,

InnoDB: the problem may be that during an earlier attempt you managed

InnoDB: to create the InnoDB data files, but log file creation failed.

InnoDB: If that is the case, please refer to

InnoDB: http://dev.mysql.com/doc/mysql/en/Error_creating_InnoDB.html

101001 20:45:09 [ERROR] Default storage engine (InnoDB) is not available

101001 20:45:09 [ERROR] Aborting

101001 20:45:09 [Note] D:\MySQL5\bin\mysqld-nt: Shutdown complete

于是去网上搜索了一下，发现提示No valid checkpoint found.的解决办法：删除所有现有的ibdataN和ib_logfileN文件后，重启Mysql。于是照做，果然行了。

InnoDB: The first specified data file D:\MySQL InnoDB Datafiles\ibdata1 did not exist:

InnoDB: a new database to be created!

101001 21:04:24  InnoDB: Setting file D:\MySQL InnoDB Datafiles\ibdata1 size to 10 MB

InnoDB: Database physically writes the file full: wait...

101001 21:04:25  InnoDB: Log file .\ib_logfile0 did not exist: new to be created

InnoDB: Setting log file .\ib_logfile0 size to 109 MB

InnoDB: Database physically writes the file full: wait...

InnoDB: Progress in MB: 100

101001 21:04:27  InnoDB: Log file .\ib_logfile1 did not exist: new to be created

InnoDB: Setting log file .\ib_logfile1 size to 109 MB

InnoDB: Database physically writes the file full: wait...

InnoDB: Progress in MB: 100

InnoDB: Doublewrite buffer not found: creating new

InnoDB: Doublewrite buffer created

InnoDB: Creating foreign key constraint system tables

InnoDB: Foreign key constraint system tables created

101001 21:04:31  InnoDB: Started; log sequence number 0 0

101001 21:04:32 [Note] D:\MySQL5\bin\mysqld-nt: ready for connections.

Version: '5.0.18-nt'  socket: ''  port: 3306  MySQL Community Edition (GPL)

奋斗了一天，总算成功地把MySQL从MyISAM转换成InnoDB引擎了。也学会了读懂错误日志文件err文件了。不过我就在想了，如果从一开始就按照上面的做，不知道会怎么样呢？