Oracle10g闪回恢复区详细解析 (2)
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<DIV class=tit6><a href=".:;" target="_blank"><FONT color=#63401b size=4 face=黑体>Oracle10g闪回恢复区详细解析 (2)</FONT></A>
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<P style="TEXT-INDENT: 2em">闪回恢复区中添加或删除文件等变化都将记录在数据库的 alert 日志中,Oracle 10g 也针对该新特性提供了一个新的视图, DBA_OUTSTANDING_ALERTS,通过该视图可以得到相关的信息。 </P>
<P> DBA_OUTSTANDING_ALERTS 视图的存在体现了 Oracle 愈加人性化的一面。我们先来看一下该视图的基本结构,后面会用到。</P>
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<TD class=“code” bgColor=#e6e6e6>SQL> DESC dba_outstanding_alerts
<P style="TEXT-INDENT: 2em"> Name Null? Type
<P style="TEXT-INDENT: 2em"> -----------------------------------------------------------
<P style="TEXT-INDENT: 2em"> SEQUENCE_ID NUMBER
<P style="TEXT-INDENT: 2em"> REASON_ID NOT NULL NUMBER
<P style="TEXT-INDENT: 2em"> OWNER VARCHAR2(30)
<P style="TEXT-INDENT: 2em"> OBJECT_NAME VARCHAR2(513)
<P style="TEXT-INDENT: 2em"> SUBOBJECT_NAME VARCHAR2(30)
<P style="TEXT-INDENT: 2em"> OBJECT_TYPE VARCHAR2(64)
<P style="TEXT-INDENT: 2em"> REASON VARCHAR2(4000)
<P style="TEXT-INDENT: 2em"> TIME_SUGGESTED TIMESTAMP(6) WITH TIME ZONE
<P style="TEXT-INDENT: 2em"> CREATION_TIME TIMESTAMP(6) WITH TIME ZONE
<P style="TEXT-INDENT: 2em"> SUGGESTED_ACTION VARCHAR2(4000)
<P style="TEXT-INDENT: 2em"> ADVISOR_NAME VARCHAR2(30)
<P style="TEXT-INDENT: 2em"> METRIC_VALUE NUMBER
<P style="TEXT-INDENT: 2em"> MESSAGE_TYPE VARCHAR2(12)
<P style="TEXT-INDENT: 2em"> MESSAGE_GROUP VARCHAR2(64)
<P style="TEXT-INDENT: 2em"> MESSAGE_LEVEL NUMBER
<P style="TEXT-INDENT: 2em"> HOSTING_CLIENT_ID VARCHAR2(64)
<P style="TEXT-INDENT: 2em"> MODULE_ID VARCHAR2(64)
<P style="TEXT-INDENT: 2em"> PROCESS_ID VARCHAR2(128)
<P style="TEXT-INDENT: 2em"> HOST_ID VARCHAR2(256)
<P style="TEXT-INDENT: 2em"> HOST_NW_ADDR VARCHAR2(256)
<P style="TEXT-INDENT: 2em"> INSTANCE_NAME VARCHAR2(16)
<P style="TEXT-INDENT: 2em"> INSTANCE_NUMBER NUMBER
<P style="TEXT-INDENT: 2em"> USER_ID VARCHAR2(30)
<P style="TEXT-INDENT: 2em"> EXECUTION_CONTEXT_ID VARCHAR2(60)
<P style="TEXT-INDENT: 2em"> ERROR_INSTANCE_ID VARCHAR2(142)
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<P style="TEXT-INDENT: 2em">SQL></P></TD></TR></TBODY></TABLE>
<P> 10g 的新视图 V$RECOVERY_FILE_DEST 包含闪回恢复区的相关信息: </P>
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<TD style="FONT-SIZE: 9pt" class=code bgColor=#e6e6e6>SQL> desc V$RECOVERY_FILE_DEST
Name Null? Type
------------------------------- ----------------------------
NAME VARCHAR2(513)
SPACE_LIMIT NUMBER
SPACE_USED NUMBER
SPACE_RECLAIMABLE NUMBER
NUMBER_OF_FILES NUMBER
SQL> SELECT NAME, space_limit, space_used, space_reclaimable space_rec,
2 number_of_files file_num
3 FROM v$recovery_file_dest;
NAME SPACE_LIMIT SPACE_USEDSPACE_REC FILE_NUM
--------------------------- ----------- ---------- ---------- ----------
/u01/app/oracle/flash_recovery_area2147483648 1106849280602410496 30
SQL></TD></TR></TBODY></TABLE>
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<P style="TEXT-INDENT: 2em">在一些 10g 的动态视图里( V$CONTROLFILE, V$LOGFILE, V$ARCHIVED_LOG, V$DATAFILE_COPY 等 )的新的列 IS_RECOVERY_DEST_FILE ,指明相关的文件是否在恢复区内。</P>
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<TD class=“code” bgColor=#e6e6e6>SQL> SELECT recid, blocks, is_recovery_dest_file
<P style="TEXT-INDENT: 2em">2 FROM v$archived_log
<P style="TEXT-INDENT: 2em">3 WHERE recid < 5;
<P style="TEXT-INDENT: 2em">
<P style="TEXT-INDENT: 2em"> RECID BLOCKS IS_RECOVERY_DEST_FILE
<P style="TEXT-INDENT: 2em">---------- ---------- -----------------------------
<P style="TEXT-INDENT: 2em"> 1 20072 YES
<P style="TEXT-INDENT: 2em"> 2 19566 YES
<P style="TEXT-INDENT: 2em"> 3 19566 YES
<P style="TEXT-INDENT: 2em"> 4 19566 YES
<P style="TEXT-INDENT: 2em">SQL></P></TD></TR></TBODY></TABLE>
<P><B> 闪回恢复区中文件的保持策略</B> </P>
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<LI>持久文件从不会被删除。
<LI>通过RMAN 配置策略过期的文件会被删除。
<LI>已经拷贝到磁带上的临时性文件会被删除。
<LI>在 Data Guard 环境中,当已归档的重作日志文件可以从闪回恢复区中删除的时候,可以应用归档的重作日志删除策略进行自动删除(在恢复管理器中CONFIGURE ARCHIVELOG DELETION POLICY TO ......)</LI></UL>
<P> 在闪回恢复区中的空间使用超过 85% 的时候,数据库将会向 alert 文件中写入告警信息。而当超过 97% 的时候将会写入严重告警信息。当闪回恢复区空间不够的时候,Oracle将报告如下类似的错误:</P>
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<TD class=“code” bgColor=#e6e6e6>ORA-19809: limit exceeded for recovery files
<P style="TEXT-INDENT: 2em">ORA-19804: cannot reclaim 52428800 bytes disk space from 1258291200 limit</P></TD></TR></TBODY></TABLE>
<P> 这个时候查询 dba_outstanding_alerts:</P>
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<TD class=“code” bgColor=#e6e6e6>SQL> select reason,object_type,suggested_action from dba_outstanding_alerts;
<P style="TEXT-INDENT: 2em">
<P style="TEXT-INDENT: 2em">REASON OBJECT_TYPE SUGGESTED_ACTION
<P style="TEXT-INDENT: 2em">------------------------------ --------------- -------------------------------------
<P style="TEXT-INDENT: 2em">db_recovery_file_dest_size ofRECOVERY AREA Add disk space and increase db_recovery_
<P style="TEXT-INDENT: 2em">1258291200 bytes is 88.20% use file_dest_size, backup files to tertiary
<P style="TEXT-INDENT: 2em">d and has 148509184 remaining device, delete files from recovery area
<P style="TEXT-INDENT: 2em">bytes available. using RMAN, consider changing RMAN rete
<P style="TEXT-INDENT: 2em"> ntion policy or consider changing RMAN a
<P style="TEXT-INDENT: 2em"> rchivelog deletion policy.
<P style="TEXT-INDENT: 2em">
<P style="TEXT-INDENT: 2em">1 rows selected.
<P style="TEXT-INDENT: 2em">
<P style="TEXT-INDENT: 2em">SQL></P></TD></TR></TBODY></TABLE>
<P> 会给出相关的原因和建议的操作。</P><B> 注意事项</B>
<P> 自动化的东西总是给人不确定性。如果您在测试环境中启用了闪回恢复区,那么一定要注意监控空间的使用。在生产数据库上使用(如果有这样的人的话),必须要把闪回恢复区放到单独的磁盘上。<BR></P></SPAN></TD></TR></TBODY></TABLE></SPAN></DIV></DIV></DIV></DIV>
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