天开始冷下来了

而我也快回北京了

在上海，我不知道该留下点什么

过去的两年，我经历了太多太多

 

不知道我还能否适应北京的气候呢？

 

不过，一切都可能会改变的

我相信。。。

 

 

忙碌了三年的项目，我毕业后的黄金三年，就在上海CUP度过了

算是得到了客户和公司领导的认可

项目组小照一张，上一会公司光荣榜，呵呵！

喜欢你的人：半夜会找你打电话聊天到很晚。 
爱你的人：半夜看你在网上会赶你下线。 
喜欢你的人：他会找你出去玩，叫你放弃正事或逃课。 
爱你的人：他会催你快写作业或者与你讨论功课。 
喜欢你的人：在你生病时，会讲好话关心你。 
爱你的人：在你生病时，他会关心到你烦，并强迫你去看医生。 
喜欢你的人：他会尽量说好话来讨好你，你也会觉得很开心。 
爱你的人：他所说的话，都是关心你的，但是通常象是在命令。 
喜欢你的人：他什么事情都会配合你，只要你开心。 
爱你的人：他会帮你辨别是非，但是你会感觉他管的太多。 
喜欢你的人：他说他要给你最大的快乐。 
爱你的人：他只能给你保证，你跟他在一起，他是最快乐的。 
喜欢你的人：他在意你的生活细节，即使你做错了什么，他也不会指出来。 
爱你的人：他在意你的一举一动，告诉你什么地方错了，什么地方该如何做，该如何与别人交往。 
喜欢你的人：他会帮你买夜宵，送夜宵，载你上下课或上下班。 
爱你的人：他会帮你买夜宵，不过会提醒你吃什么比较健康；他会载你上下课或上下班，但通常是顺路；因为他不会为了你而逃课或旷工。因为他知道，他要为你们的将来而努 
喜欢你的人：他不会在意你去做什么，与什么人交往。 
爱你的人：他很在意你去做什么，与什么人交往。他还会告戒你不要与什么人交往 
喜欢你的人：他只想要现在 
爱你的人：他已经预见未来，该怎么自我努力，好好给你幸福。 
喜欢你的人：他会说“我喜欢你！” 
爱你的人：他会说“我爱你！！！“ 

昨晚继续借室友HANA的被子，早早就睡着了，还是半夜热醒了好几次，还是强迫自己睡着

早晨起来，感觉轻松了很多，虽然还有点咳嗽，鼻子还有点不听使唤

但是对比昨天来说，好了很多了

谢谢小静的问候，朋友的关怀之情，是不是比药物什么的更加有效呢？

 

早晨起来，想看火箭对灰熊队的季前赛，可是，比上海体育忽悠了，到8:30什么都没有，害得我球没看到，早餐没吃成

一到公司，就被客户那边的经理拉住

oh，my god，要我培训他们新来的几位同事

希望她们都是有专业基础的，不然我就惨了！

期待中。。。

 

吃饭时间到咯，有点饿，不写了，吃饭去，下午还得继续看我那个烦躁的英文文档，考试啊。。。

How Does Prefetching Work?

Prefetching will be requested by a DB2 agent if the access plan has specified that prefetching should be done or if sequential detection is enabled and a number of pages are read in sequence. The DB2 agent will make prefetch requests that will be examined by the prefetch manager and assigned to the DB2 I/O servers (also known as prefetchers).

The prefetch requests are sent to a queue where they are examined by the prefetch manager. The prefetch manager examines the requests to determine whether any of the prefetch requests from different applications can be combined and handled more efficiently in one prefetch operation. If no prefetch requests can be combined, the queue acts in a first in-first out (FIFO) manner.

To ensure that the prefetchers do not work too aggressively, reading data into the buffer pool and overwriting pages before they can be accessed, the amount of prefetching is controlled by the size of the buffer pool, as well as the prefetch size and the access plan generated by the optimizer. For smaller buffer pools, prefetching may be scaled back to ensure that prefetched pages do not flood the buffer pool and kick out pages that are currently being used or have been prefetched into the buffer pool and have not been accessed.

Within DB2 UDB, there are two main types of data and index prefetch requests handled by the prefetchers: range and list prefetching.

Range prefetching is used to prefetch a sequential range of pages from a database object and is used during table scans and when triggered by sequential detection. If a block-based area is set aside in the buffer pool, DB2 will perform a "big block" read to read a contiguous series of pages into a single private memory buffer, then will copy the block of pages to the block-based area of the buffer pool with one memory copy operation.

Internally, the mechanism used is big block read or "vectored" read (on platforms that support an efficient vectored read API). A big block read involves reading a contiguous block of pages into a single, private memory buffer. Each individual page is then copied into its own buffer pool slot (and all of these slots are likely to be scattered throughout the buffer pool). A vectored read API will read a contiguous block of pages from disk into different memory buffers (a different memory buffer for each page of the block). In this case, those memory buffers can actually be the individual buffer pool slots, and the overhead of the copy from one memory buffer to another is avoided (hence, an efficient vectored read API is preferred over big block read). The block-based area of the buffer pool overcomes this by setting aside contiguous blocks of the buffer pool equal in size to the extent size to make prefetching more efficient, especially on operating systems that do not support vectored reads.

List prefetching is used to prefetch a list of pages into the buffer pool area when an index scan produces a list of record IDs (RIDs) that must be prefetched into the buffer pool. List prefetching is normally decided on and specified in the access plan when the SQL statement is optimized. A list prefetch request may get converted to a range prefetch request if the pages are found to be sequential.

There is one prefetch queue that is monitored by the prefetch manager and shared between all of the configured prefetchers. The prefetch queue can handle up to 100 prefetch requests.

When a prefetch request is made, the request will be broken up into a number of smaller I/O requests. By default, the number of I/O requests will be determined by the number of containers that are in the table space. However, if the DB2_PARALLEL_IO registry variable is set, DB2 will start up a number of prefetchers equal to the prefetch size divided by the extent size. This allows multiple prefetchers to be working on the requests in parallel.

还是不太懂？还打算这个月底考试呢，怕是够呛咯！

加油！

我病了，感冒，周一上午坚持去体检，下午就在家睡了

感谢两位室友的照顾，今天可以坚持来上班了

 

真希望自己身边有那个人

和我陪伴互相照顾一辈子的那个人

四年的北京大学生活，毕业三年，在上海出差2年半

office在北京，但是户口在上海

大部分朋友在北京，上海就那么几个

北京气候很干燥，但是我已经适应；上海气候很湿润，我更喜欢

北京是首都，从小就向往的地方；上海是开发大城市，梦可以起飞的天堂

北京有我大学时代的回忆，上海有我工作后的回味

 

离回北京的时间越来越近，可是我越来越分不清楚，我到底该留在哪里？

一直都对自己说，哪里有我人生的那个人，我就在哪里

可是，一切都不可先定

计划赶不上变化，我一个朋友说的

那就不用想，好好珍惜现在的日子

不管到了哪里，你永远是最亮的那颗星！

 

 

How Many Buffer Pools Should a Database Have?

There are two main schools of thought regarding the number of buffer pools that should be configured for a database:

• Use one big buffer pool and let DB2's aging algorithm take care of which pages are in the buffer pool.

• Use multiple buffer pools and assign them to specific table spaces to ensure that highly active pages are kept in the buffer pool.

If DB2 is installed in 32-bit mode, there are limitations on the maximum amount of shared memory that can be addressed by a process. Because the buffer pool is allocated in shared memory, there are limits on the maximum size of the buffer pool(s) that can be created for a database, regardless of the amount of physical memory on the system. If DB2 is installed in 64-bit mode, the shared memory limit is much higher, and most systems will run out of real memory before hitting the operating system limit.

If they are properly sized and assigned to the right table spaces, multiple buffer pools will outperform a single buffer pool. However, multiple buffer pools will require constant monitoring and tuning in order to keep them performing optimally.

Other than its size, a single buffer pool needs no tuning. DB2 has a highly optimized algorithm for aging pages in the buffer pool that uses several techniques designed to optimize the buffer pool hit ratio by:

• Favoring important pages, such as index pages

• Placing pages that are unlikely to be accessed again on "Hate stacks," which are used to identify victim pages quickly

昨天，我度过了25岁的生日

呵呵，同事说，男人越老越值钱，我看这样安慰自己挺好的

 

陆续收到了一些朋友的生日祝福，很开心

小玉给我买了一个很大的生日蛋糕，有点感动

室友几个一起吃还没吃完

今天回家还得加把劲哦

 

想起一位名人说过的一句话，说得是朋友之间的关系的，呵呵，对不起，是什么突然忘记了

 

一早收到弟弟的生日祝福短信和妈妈的电话，我想哭，但是我坚持，在她面前，我不能哭

我的家人，是我唯一可以依靠的人

 

呵呵，今天，是我26岁的第一天了，是否也该特殊一点呢？

 

 

明天，不知道谁会记得我?