查看回滚段的使用情况，，哪个用户正在使用回滚段的资源select s.username, u.name from v$transaction t,v$rollstat r,v$rollname u,v$session s where s.taddr=t.addr andt.xidusn=r.usn and r.usn=u.usn order by s.username;检查UNDO Segment状态select usn,xacts,rssize/1024/1024/1024,hwmsize/1024/1024/1024,shrinksfrom v$rollstat order by rssize;确定当前例程正在使用的UNDO表空间Show parameter undo_tablespace显示数据库的所有UNDO表空间SELECT tablespace_name FROM dba_tablespaces WHERE contents=’UNDO’;显示UNDO表空间统计信息SELECT TO_CHAR(BEGIN_TIME,’HH24:MI:SS’) BEGIN_TIME,TO_CHAR(END_TIME,’HH24:MI:SS’) END_TIME,UNDOBLKSFROM V$UNDOSTAT;显示UNDO段统计信息SELECT a.name, b.xacts, b.writes, b.extentsFROM v$rollname a, v$rollstat bWHERE a.usn=b.usn;显示活动事务信息Col username format a10Col name format a10SELECT a.username, b.name, c.used_ublkFROM v$session a, v$rollname b, v$transaction cWHERE a.saddr=c.ses_addr AND b.usn=c.xidusnAND a.username=’HR’;V$ROLLSTAT中的常用列USN Rollback segment numberEXTENTS Number of extents in the rollback segmentRSSIZE Size (in bytes) of the rollback segment.WRITES Number of bytes written to the rollback segmentXACTS Number of active transactionsGETS Number of header getsWAITS Number of header waitsOPTSIZE Optimal size of the rollback segmentHWMSIZE High-watermark of rollback segment sizeSHRINKS Number of times the size of a rollback segment decreasesWRAPS Number of times rollback segment is wrappedEXTENDS Number of times rollback segment size is extendedAVESHRINK Average shrink sizeAVEACTIVE Current size of active extents, averaged over time.STATUS Rollback segment status: ONLINE PENDING OFFLINE OFFLINE FULLCUREXT Current extentCURBLK Current block
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