Sometimes MySQL Replication may run out of sync - because of its own buts or operational limitations or because of application mistake, such as writing to the slave when you should be only writing to the master. In any case you need slave to be synced with Master.

To discover the difference between Master and Slave you can use excellent Maatkit tool though if you you just need to resync small single table it may be easy to do it other way:

Assuming your table schema does not change you can do something like this on the master:

LOCK TABLE tbl WRITE;
SELECT * FROM table INTO OUTFILE '/tmp/tbl.txt';
DELETE FROM tbl;
LOAD DATA INFILE 'tmp/tbl.txt' INTO TABLE tbl;
UNLOCK TABLES;

This will dump master's table content to the file clean the table on master and slave and refresh it on both of them.

This obviously makes table inaccessible on master for duration of operation but for small tables it can take just few seconds.

This trick is of course quite dirty, especially if you're dealing with sensitive data - what if you run out of space or SELECT INFO OUTFILE fails for other reason and you proceed with deletion you may kiss your data goodbye.

Alternative would be not to drop the table but rather raname them. Unfortunately you can't rename locked tables (ERROR 1192 (HY000): Can't execute the given command because you have active locked tables or an active transaction) - this is also I used DELETE instead of TRUNCATE to clean out the table.

In the applications which are error tolerant (like handle errors properly) you may rename table instead of locking - for many applications this works better anyway as having table locked causes connections to pile up and either MySQL runs out of connections or Apache out of children allowed to process request;

So you can do following instead:

This way you never actually delete any data and besides same data loaded to "rep" table you will get the copy of old table in "rep_old" - this can be very handy if you would like to later investigate why data got out of sync and may be do some manual touch ups after you resync the data.

Note - this process works well for small tables when you do not want to shut down the master and slave. If you need quick resync of large amount of data it is much better to use LVM snapshots or similar techniques - these are much faster.

Entry posted by peter | No comment

Add to: | | | |

VirtualBox, Virtual PC, VMware Workstation and a few other software packages help you create and run multiple virtual machines on your desktop or laptop enabling you to run multiple operating systems simultaneously on a single computer.

My personal favorite is VirtualBox (recently acquired by Sun Microsystems), not only because it is freely available as Open Source Software and runs on Windows, Linux and Macintosh but also because it has great features and supports a large number of guest operating systems.

Last Saturday I used VirtualBox to create a new virtual machine (VM) running Windows XP Pro and Oracle Database 11gR1. First, I created a “base” VM with only Windows XP pro SP3 installed. I then detached the virtual disk file (VDI) from the VM. I ended up with a VDI file that I can clone as many times as I want eliminating the need to install a new operating system every time I create a new VM.

Cloning a virtual disk in VirtualBox is done using the command line. For example, to clone WindowsXP.vdi as a new virtual disk called WindowsXPProOraDB11gR1.vdi, you would issue this command:

VBoxManage clonevdi WindowsXP.vdi WindowsXPProOraDB11gR1.vdi

You would then assign WindowsXPProOraDB11gR1.vdi as the virtual hard drive of a new virtual machine.

The installation of Oracle Database 11gR1 on a new Windows XP VirtualBox VM on my laptop went very smoothly, but I had to troubleshoot a couple of things on the VM: A missing loopback adapter and a 100% CPU usage.

My laptop and the newly created VM do not have a static IP address. Dynamic Host Configuration Protocol (DHCP) is used to assign dynamic IP addresses on the network. According to the documentation, before installing Oracle Database onto a computer that uses the DHCP protocol, you need to install a loopback adapter to assign a local static IP address to that computer. I followed the instructions found in the Oracle Database Pre-installation Requirements document to install the loopback adapter. After that, the database installed without any issues.

Now that my WinXP VM and 11g Database are up and running, I noticed that the oracle.exe process was consuming 100% of the CPU. I waited a few minutes, but the CPU usage did not go down, it stayed at 100%. After a quick search, I found these two forum posts: post 1 and post 2. Since this is a test database, I did not hesitate to follow the instructions in post 2 and was able to bring the CPU usage down to a normal level.

Virtual machines are a great way to learn and try new software and applications without the need to buy new hardware or messing up your existing computer. You may even have fun embarking on some virtual adventures.

---
Related Articles at Eddie Awad's Blog:

• Goodbye 2005, Hello Vegas
• The Oracle Community on Twitter
• Ubuntu on Microsoft Virtual PC Works Like a Charm
• Indirect Privilege Escalation And Defeating Virtual Private Databases
• Oracle Metalink Firefox search plugin

7月1日下午我会去朝阳区亚运村法庭领传票，这一次的开庭应该是在7月初的某一天，具体日期等领到传票再公布。
希望这是最后一次开庭。

©作者：eygle 发布在 eygle.com

关于精彩部分就不说了，我要说说 熊猫阿宝的五溪指法，阿宝最后通过自悟的指法击败了残豹，那么这指法是如何来的呢？
师傅当初是没有教过的，我相信有这样一种无师自通的领悟，Panda在不断的练习和战斗中熟练并且成为一个挥洒自如，充分发挥自身潜质的功夫高手，这些使他具备了自由发挥与创造的基础。
终于Panda使出了核武器一样的超级指法。

其实在残豹和师傅斗争中，我一直期望能够有另外一种结局，残豹从一只可爱的小豹子成为一个充满野心与暴力的复仇者，很多人应该对此负责，甚至在Panda与残豹的决斗中，我也期待能有一种回归的结局，但是这种结局没有出现，因为电影需要有一个对立面的存在。

无师自通与忽然的领悟，每个人都需要这样的时刻。

有一些台词很值得回味，网上找到了几条：
1.往往在逃避命运的路上，却与之不期而遇
One meets its destiny on the road he takes to avoid it
2.你的思想就如同水，我的朋友，当水波摇曳时，很难看清，不过当它平静下来，答案就清澈见底了。
Your mind is like this water, my friend , when it is agitated ,it becomes difficult to see ,but if you allow it to settle , the answer becomes clear.
3.退出，不退出。做面条，不做面条。
Quit don't quit. Noodles don't noodles.
4.昨天是历史，明天是谜团，只有今天是天赐的礼物
Yesterday is history
Tomorrow is a mystery
But today is a gift
That is why it's called the present (the gift)
5.从来没有什么意外
There are no accidents
6.师傅：但有些事情我们可以控制，我可以控制果实何时坠落，我还可以控制在何处播种。
but there are things we can control，I can control when the fruit will fall ... And I can control What time to seed

-The End-

相关文章|Related Articles

• 推荐电影《Juno》-朱诺
  
• 《越狱》第三季之Sara之死
  
• 从《越狱》（Prison Break）看中美差异
  
• 今天买入的几本图书
  
• 连杰老去 元甲收山
  

评论数量(3)|Add Comments

本文网址：http://www.eygle.com/archives/2008/06/kongfu_panda.html