Adaptive Log File Sync In 11gr2 (_use_adaptive_log_file_sync)

Adaptive Log File sync was introduced in 11.2. the feature is exactly enabled since release 11.2.0.3 , It’s enabled through an underscore parameter called _use_adaptive_log_file_sync and the description of this parameter is: adaptively switch between post/wait and polling. Oracle can switches between the 2 methods: Post/wait, traditional method for posting completion of writes to redo … Read more

jboss 占用高cpu 的诊断思路

top – 14:32:11 up 104 days, 20:27, 1 user, load average: 19.31, 19.10, 19.06 Tasks: 390 total, 19 running, 371 sleeping, 0 stopped, 0 zombie Cpu(s): 99.5%us, 0.1%sy, 0.0%ni, 0.4%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 8164276k total, 8111804k used, 52472k free, 403596k buffers Swap: 16386292k total, 224k used, 16386068k free, 5560532k cached [root@webxxx ~]# ps … Read more

Logon Storm and Memory shortage issue ORA-07445 dbgtrReserveSpace (记录一次登录风暴致内存不足的问题)

Exception [type: SIGSEGV, Address not mapped to object] [ADDR:0x10] [PC:0x938E8C5, dbgtrReserveSpace()+99] [flags: 0x0, count: 1]
Errors in file /oracle/diag/rdbms/ora11g/ora11g/trace/ora11g_ora_13864.trc (incident=60801):
ORA-07445: exception encountered: core dump [dbgtrReserveSpace()+99] [SIGSEGV] [ADDR:0x10] [PC:0x938E8C5] [Address not mapped to object] []
Incident details in: /oracle/diag/rdbms/ora11g/ora11g/incident/incdir_60801/ora11g_ora_13864_i60801.trc
Use ADRCI or Support Workbench to package the incident.

scn format (scn格式)

scn(system change number) 结构主要维护 oracle数据库内部的数据一致性,SCN 有两部分组成: Base and wrap,wrap 是16bit的数字,base是32bit的数字,这样其实就可以算scn的有效范围,它的格式(redo dump trace)是wrap.base,当base超过了2的32次方,然后wrap 就会加1,其实用sql 很好验证。