kramer

摘要：光圈特性（一）：控制进光量 光圈作为相机镜头内的一个元件，它的作用是控制透过镜头进入机身内感光元件的光量，所以光圈的一大功能就是控制进光量的多少。一般来说完整的光圈值系列如下：f1.0，f1.4，f2.0，f2.8，f4.0，f5.6，f8.0，f11，f16，f22，f32，f44，f64。我们可以通过一张简单的示意图来说明不同数值的光圈和它孔径大小的关系。这里值得一提的是光圈 f 值越小，通光孔径越大（如上图所示），在同一单位时间内的进光量便越多，光圈 f 值越大，通光孔径越小，在同一单位时间内的进光量便越少，而且上一级的进光量刚好是下一级的两倍，例如光圈从F8调整到5.6 ，进光量便多. 阅读全文

摘要：要说什么是ISO还要从传统胶片相机说起，ISO称作为感光度，它是衡量传统相机所使用胶片感光速度的国际统一指标，其反映了胶片感光时的速度（其实是银元素与光线的光化学反应速率）。而对于现在并不使用胶片的数码相机来说，其成像原理是通过感光器件CCD或CMOS以及相关的电子线路感应入射光线的强弱来进行成像的。为了与传统相机所使用的胶片统一计量单位，这才引入了ISO感光度的概念。在数码相机中ISO同样也反应了相机感光元件的感光速度。在传统的胶片相机时代，我们可以因拍摄环境亮度的不同来选购不同感光度(ISO)的底片，例如一般晴天环境可使用ISO100，阴天的环境可用ISO200，黑暗如舞台，演唱会等环境可 阅读全文

摘要：Today when trying to open my Oracle EM url, I can not open it. So I thought may be the network is having issue. I use the tenlet to try to identifiy if the network is ok. The command is telnet racnode1 1158 and it shows the network is ok. So I go to the the rac server to check.First I use emctl stat 阅读全文

摘要：backup terminologyUsing the RMAN BACKUP Commandto Create BackupsServer-Managed Consistent Backupsserver-managed open backupsincremental backupsimage copyprotect your backupsparallelism your backupsconfig rman defaultsManaging and Monitoring RMAN BackupsThe LIST, REPORT, and DELETE CommandsArchival B 阅读全文

摘要：v$log has one row for each group.v$logfile has one row for each file.There is a status column for v$log.Current means the group is being used.Inactive means the group is not in use and will not be need for instance recovery if the instance crash now.Active means the group is not in use but will be u 阅读全文

摘要：Release 9i introduced a new parameter, FAST_START_MTTR_TARGET, that makes controlling instance recovery time a trivial exercise. You specify it in seconds, and Oracle will then ensure that DBWn writes out blocks at a rate sufficiently fast that if the instance crashes, the recovery will take no long 阅读全文

摘要：You can use bellow command to make your session resumable. Which means that if your session hit space limited issue, for example, the data file do not have more space and it can not be auto extended, then your session will not exit with error. It will only hung there waiting for you to resolve the i 阅读全文

摘要：First of all, the version of my enviroment is Oracle 11.0.2.3. The fast recovery area used to be called flashback recovery area. When you want to enable flashback database feature, your database must have this area. So I always confused about these two concept.Let`s review how to enable flashback re 阅读全文

摘要：在尝试删除一个diskgroup的时候遇到这个错误。ORA-15024: discovered duplicately numbered ASM disk 0这说明oracle认为有两个disk 具有相同的ID。 好像是这么个意思。虽然不知道这是为什么，但是却非常容易解决dd if=/dev/zero of=data01 bs=1024 count=100用上面这条命令把该diskgroup中的每一个diskgroup磁盘头信息清空。 这样就可以删掉[oracle@racnode1 nfsdg1]$ dd if=/dev/zero of=data01 bs=1024 count=100100+ 阅读全文

摘要：本文基于oracle 11.0.2.3. 主要介绍什么叫Qos management。本文包括以下内容：什么是 Oracle Database QoS Management?使用QoS Management的好处Overview of Oracle Database QoS ManagementWhat Does Oracle Database QoS Management Manage?Overview of Metrics什么是 oracle database Qos management现在企业里倾向于把多个不同业务的数据库整合到一起，用一个数据库面向多种应用需求。比如说，人力资源管理业 阅读全文

摘要：首先，这是oracle 11g 11.0.2.3 版本。这是一个神奇的问题.asm instance启动正常，但是用sqlplus 去连接的时候会显示如下：[oracle@racnode1 ~]$ sqlplus / as sysasmSQL*Plus: Release 11.2.0.3.0 Production on Fri Sep 6 12:59:28 2013Copyright (c) 1982, 2011, Oracle. All rights reserved.Connected to an idle instance.SQL> quitView Code 这是因为 ORACL 阅读全文

摘要：Hit an strange error just now.[oracle@racnode1 ~]$ srvctl## An unexpected error has been detected by HotSpot Virtual Machine:## SIGBUS (0x7) at pc=0x42604f0a, pid=20424, tid=3077707456## Java VM: Java HotSpot(TM) Client VM (1.5.0_30-b03 mixed mode, sharing)# Problematic frame:# /u01/app/11.2.0/grid. 阅读全文

摘要：overview of different flashback technologiesflashback query(including flashback query, flashback version query , flashback transaction, flashback table)flashback dropflashback databaseflashback data archiveoverview of different flashback technologiesFirstly this chapter is writen based on oracle 11g 阅读全文

摘要：首先设置 archive log的位置SQL> alter system set log_archive_dest='+DATA/orcl/archive/';System altered.这个设置要在两个instance上都进行其次是要重启数据库到mount状态[oracle@racnode1 ~]$ srvctl stop database -d orcl -o immediate[oracle@racnode1 ~]$ srvctl start database -d orcl -o mount这个只在一个节点运行即可。接下来需要进入数据库设置archive mod 阅读全文