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桌面->右键->属性->外观->高级－>项目选择（窗口）、颜色1（L）选择（其它）将色调改为：85。饱和度：123。亮度：205－>添加到自定义颜色－>在自定义颜色选定点确定－>确定. 这样所有的文档都不再是刺眼的白底黑字，而是非常柔和的豆沙绿色，这个色调是眼科专家配置的，长时间使用会很有效的缓解眼睛疲劳保护眼睛. [@more@]

A baseline is created with the CREATE_BASELINE procedure. A baseline is simply performance data for a set of snapshots that is preserved and used for comparisons with other similar workload periods when performance problems occur. You can review the existing snapshots in the DBA_HIST_SNAPSHOT view to determine the range of snapshots that you want to use. For example:BEGIN DBMS_WORKLOAD_REPOSITORY.CREATE_BASELINE (start_snap_id => 270, end_snap_id => 280, baseline_name

For example:BEGIN DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS( retention => 43200, interval => 30, topnsql => 100, dbid => 3310949047);END;/setting affects how often in minutes that snapshots are automatically generated. The RETENTION setting affects how long in minutes that snapshots are stored in the workload repository. The TOPNSQL setting affects the number of Top SQLto flush for each SQL criteria (Elapsed Time, CPU Time, Parse Calls, Shareable Memory, and

You can drop a range of snapshots using the DROP_SNAPSHOT_RANGE procedure. To view a list of the snapshot Ids along with database Ids, check the DBA_HIST_SNAPSHOT view. For example, you can drop the following range of snapshots:BEGIN DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE (low_snap_id => 22, high_snap_id => 32, dbid => 3310949047);END;/In the example, the range of snapshot Ids to drop is specified from 22 to 32. The optional database identifier is 33109

You can manually create snapshots with the CREATE_SNAPSHOT procedure if you want to capture statistics at times different than those of the automatically generated snapshots. For example:BEGIN DBMS_WORKLOAD_REPOSITORY.CREATE_SNAPSHOT ();END;/In this example, a snapshot for the instance is created immediately with the flush level specified to the default flush level of TYPICAL. You can view this snapshot in the DBA_HIST_SNAPSHOT view.[@more@]

Some pitfalls are discussed in the following sections:■ Hit ratios■ Wait events with timed statistics■ Comparing Oracle statistics with other factors■ Wait events without timed statistics■ Idle wait events■ Computed statistics[@more@]

CPU : sar, vmstat, mpstat, iostatMemory : sar, vmstatDisk : sar, iostatNetwork : netstat[@more@]

Measure the normal performance of the I/O system; typical values for a single block read range from 5 to 20 milliseconds, depending on the hardware used. If the hardware shows response times much higher than the normal performance value, then it is performing badly or is overworked. This is your bottleneck. If disk queues start to exceed two, then the disk is a potential bottleneck of the system. 正常的磁盘读取单个数据块在5-20毫秒之间.如果disk queues超过2个,那么磁盘有可能成为系统的瓶颈[@more@]

Operating system statistics include the following:■ CPU Statistics■ Virtual Memory Statistics■ Disk Statistics■ Network Statistics[@more@]

On an Oracle data server system, where there is generally only one application running, the server runs database activity in user space. Activities required to service database requests (such as scheduling, synchronization, I/O, memory management, and process/thread creation and tear down) run in kernel mode. In a system where all CPU is fully utilized, a healthy Oracle system runs between 65% and 95% in user space. The V$OSSTAT view captures machine level information in the database, making it

■ 1 - User■ 2 - Redo■ 4 - Enqueue■ 8 - Cache■ 16 - OS■ 32 - Real Application Clusters■ 64 - SQL■ 128 - Debug不明白我自己机器上还有class为40,72的是什么意思[@more@]

The data present in ASH can be rolled up on various dimensions that it captures, including the following:■ SQL identifier of SQL statement■ Object number, file number, and block number■ Wait event identifier and parameters■ Session identifier and session serial number■ Module and action name■ Client identifier of the session■ Service hash identifier[@more@]

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This statistics represents the total time spent in database calls and is a indicator of the total instance workload. It is calculated by aggregating the CPU and wait times of all sessions not waiting on idle wait events (non-idle user sessions). DB time is measured cumulatively from the time that the instance was started. Because DB time it is calculated by combining the times from all non-idle user sessions, it is possible that the DB time can exceed the actual time elapsed since the instance s

可从V$SESS_TIME_MODEL或者V$SYS_TIME_MODEL动态视图中获得时间类指标的统计数据.V$SESS_TIME_MODEL displays the session-accumulated time for various operations. The time reported is the total elapsed or CPU time (in microseconds). Any timed operation will buffer at most 5 seconds of time data. Specifically, this means that if a timed operation (such as SQL execution) takes a long period of time to perform, the data published to this view is at most missing 5 seconds of the time accumulated for the op

To enable easier high-level analysis of the wait events, the events are grouped into classes. The wait event classes include: Administrative, Application, Cluster, Commit, Concurrency, Configuration, Idle, Network, Other, Scheduler, System I/O, and User I/O.The wait classes are based on a common solution that usually applies to fixing a problem with the wait event. For example, exclusive TX locks are generally an application level issue and HW locks are generally a configuration issue. The follo

据分析,2007年,中国移动用户数为38660万户,铁通有固定电话用户2079万户和475万互联网用户,合并后用户总数超过4.11亿.这是新移动的客户资源.2007年,中国联通CDMA用户有4192.6万户,中国电信固定电话加小灵通用户共有2.26亿户.合并后用户总数可以达到2.67亿户.此外,中国电信还有3817万户互联网宽带接入用户,用户数超过3个亿.2007 年,中国联通GSM用户有12056.4万户,中国网通固定电话加小灵通用户有11878万户,电话用户总数可以达到23934万户,即约为2.39亿用户.此外,中国网通还有互联网宽带用户2600多万,合并后用户数超过2.6亿.[@more@]

You can modify, drop columns from, or rename a temporary table. However, for a temporary table you cannot:■ Add columns of nested table type. You can add columns of other types.■ Specify referential integrity (foreign key) constraints for an added or modified column.■ Specify the following clauses of the LOB_storage_clause for an added or modified LOB column: TABLESPACE, storage_clause, logging_clause, allocate_extent_clause, or deallocate_unused_clause.■ Specify the physical_attributes_clau

参阅http://www.orafaq.com/node/1902[@more@]

http://luckysea.itpub.net/post/5481/323246cache buffers chains当一个数据块读入sga区，相应的buffer header会被放置到hash列表上,我们称其这hash chains,chain在中文的意为链条或串的意思，表达就是关连性.如果一个进程想访问或修改hash chain上的block,它首先要获得"cache buffers chains" latch。cache buffers chains latch等待高大体有两个方面：1、写的比较差的sqlcache buffers chains latch很大程度与逻辑读有关，所以要观注v$sql中BUFFER_GETS/EXECUTIONS大的语句。同时每一个逻辑读需要一个latch get 操作及一个cp