DB2的锁 DB2的锁实现机制很复杂，它没有实现类似Oracle的undo机制，导致操作之间容易阻塞， 比如你经常会听到有人说DB2查询阻塞更新

HotSpot GC 对于Java应用的优化，GC是重要的一环，而读懂GC日志是调优GC的关键，本文尝试对GC 做一些解读，测试使用的JVM版本是1.6.0_4

Oracle AWR Automatic Workload Repository gathers, processes and maintains performance stats used for problem detection and self-tuning the databases. This collective information can be displayed as views and reports (HTML/text) to better show the current database performance status for further analysis. AWR gathers the following data: 1. Object Statistics (access / usage stats of DB segments) 2. Time Model Statistics (V$SYS_TIME_MODEL and V$SESS_TIME_MODEL views) 3. Some of the System and

硬盘IOPS[fn:3][fn:4] | size | RPM | Seek time | Avg Rota latency | Throught | Random IOPS | | | | | 0.5/(RPM/60) | | 1/(seek+latency) | |——+——-+———–+——————+———-+——————| | 2.5 | 15000 | 4ms | 2ms | 6Gbps | ~175-210 | | 2.5 | 10000 | 4ms | 3ms | 6Gbps | ~175-210

Strace notes strace是linux下的一个进程trace工具，通过strace，能够trace进程的所有系统调用， 对于解决一些棘手问题有很大帮助。