EVALUATING A SYSTEM’S PERFORMANCE
Operational software was designed to improve the efficiency of computer systems．DP professionals are constantly looking for signs that their computer hardware is not performing effectively．Processing delays，slow response times，frequent error states，and longer processing cycles are just a few of the signs of malfunctioning operational software．Examples of these types of inefficiencies are readily apparent in online processing systems．File inquiries that normally might take fractions of seconds now require seconds to complete．Processing time for programs in the job increases by 20 to 40 percent for no apparent reason[1]．There are complaints about increased response times in both peak and off-peak periods．These and other operational difficulties may signal that an operating system is under stress．
Though these examples may indicate inefficiencies in the operational software，they are insufficient for the systems programmer monitoring that performance．Programmers need more precise operational data upon which to base their analyses and evaluations．
Manufacturers accordingly modified their operational software to provide such statistics．This area of specialization，known as performance management，provides the data needed to evaluate a system’s level of performance．The performance management software is built into the operating system and can provide statistics relating to：
（1）The number and type of I / O operations and time required to perform them．
（2）The volume and frequency of access to files in the entire system．
（3）The average response time needed to handle online inquiries．
（4）The frequency of access to specific disk drives and the files maintained on that device．
（5）The volume of telecommunication traffic handled by specific channels．
（6）The usage times associated with all I / O devices．
（7）The amount of available CPU space during peak periods．
（8）The average time needed to process a tast in the job queue，broken down into waiting time and actual processing time．
（9）The frequency of use of the system’s utility software．
（10）The frequency of execution for all software run with the system．
These statistics can advise the systems programmer on the system’ s overall performance level．They are compared against earlier performance data and accepted norms（for that type of computer hardware）to determine whether the system is operating efficiently．This data helps system programmers decide if the existing perational software should be modified or whether a new operating system must be installed．
For example，performance management statistics may reveal that one disk drive is repeatedly used while others remain idle．This condition slows performance，as most of the drive’s actions relate to movement of the access arm，not file handling．It may also signal that two high-usage files are on the same disk and should be moved to separate drives[2]．The performance data may reveal that the telecommunications services supporting a user facility may be inadequate for their existing workload[3]．This often occurs as operational demands on an organization grow and shift in response to user and customer needs [4]．
NOTES
[1] 此句中“increasees by 20 to 40”意思是“增加了20% ~ 40%”。
[2] “should be moved to separate drives”是表示与现在相反的虚拟语句，“should be”常译为“本（应）该”。
[3] “that”到句末是由“that”引导的宾语从句；其中，“supporting a user facility”是现在分词短语，作定语修饰“the telecommunications services”。
[4] “shift”本意为“转移，改变”。
KEYWORDS
performance management 性能管理
operational software 操作软件
file inquiries 文件查询
online inquiries 联机查询
DP（Data Processing） 数据处理
翻译：
操作软件是为了提高计算机系统的效能而设计的。数据处理专业人员经常寻找计算机硬件不能有效运行的征兆。处理延迟，响应过慢，频繁出错，以及处理周期过长，正是操作软件误动作的几种征兆。这几类低效现象在联机处理系统中容易发生。文件查询在正常情况下只需若千分之一秒钟，现在则需数秒钟。没有明显理由，作业中程序的处理时间增加了20%~40％，还存在响应时间在高峰期和非高峰期都要增加的问题。这些和其他操作困难可能标志着操作系统出现麻烦。
尽管这些例子可能表明操作软件低效，但对监测系统性能的系统程序员来说还不够充分。程序员需要更准确的操作数据作为分析和评价的依据。
相应地，厂家修改其操作软件以产生此类统计数字。这一特殊的领域称为性能管理，它提供了评价系统性能水平所需的数据。将性能管理软件装入操作系统，能提供有关下列各项的统计数字：
（1） I/O操作的数量和种类及完成这些操作所需时间；
（2）访问整个系统文件的数量和频率；
（3）处理联机查询的平均响应时间；
（4）访问特定磁盘驱动器及其所维护文件的频率；
（5）由特定通道处理的远程通信的通信量；
（6）与所有I/O设备相关的使用时间；
（7）峰值期CPU的可用空间大小；
（8）处理作业队列中一个任务的平均时间，其中等待时间和实际处理时间分别统计；
（9）系统实用软件的使用频率；
（10）系统所有运行软件的执行频率。
这些统计数字为系统程序员提供了系统总体性能水平的数据。系统程序员将它们与原来的性能数据和已经认可的额定值（对于同种类型的硬件）相对比，以判定系统是否有效运行。这个数据有助于系统程序员确定是否需要修改现有操作软件，或是否必须安装新的操作系统。
例如，性能管理统计数字可以表明只有一个磁盘驱动器重复工作而其他驱动器处于空闲状态，这种情况会降低性能，因为驱动器的大部分动作与取存臂的移动有关，而与文件处理无关。统计数字还可揭示两个频繁使用的文件存储在同一磁盘内，应移向两个分离驱动器。性能数据会揭示由于用户所使用的电信设施不能满足用户现有工作负荷而产生的问题。当一个机构的操作需求量为对用户要求作出响应而增加时，这种情况经常发生。
EXERCISES
Fill in the blanks with appropriate words or phrases．
（1）Operational software was designed to improve ．
（2）Inefficiencies in the operational software can be exampled by ．
（3）File inquiry might normally take ．
（4）The average time needed to process a task in the job queue involves ．
（5）Most of the drive’s actions do not relate to ．
（6）To analyze and evaluate the performance of a operational software programmers need ．
（7）We have listed types of statistics describing system’s overall performance level．
（8）Some complaints and operational difficulties may signal that ．
（9） is built into the operating system．
（10）Statistics can help system programmers determine if should be modified or whether must be installed．
a．processing delays，slow response times，frequent error states，and longer processing cycles
b．more precise operational data
c．existing operational software，a new operating system
d．the efficiency of computer systems
e．10
f．fractions of seconds
g．Performance management software
h．file handling
i．an operating system is under stress
j．waiting time and actual processing time
答案：
（1）d
（2）a
（3）f
（4）j
（5）h
（6）b
（7）e
（8）i
（9）g
（10）c