SYS@orcl11galter database datafile 6 online;alter database datafile 6 online*ERROR at line 1:ORA-01113: file 6 needs media recoveryORA-01110: data file 6: /opt/oracle/oradata/orcl11g/zbdba01.dbf 有时候我们数据文件offline之后,再online需要
SYS@orcl11g>alter database datafile 6 online; alter database datafile 6 online * ERROR at line 1: ORA-01113: file 6 needs media recovery ORA-01110: data file 6: '/opt/oracle/oradata/orcl11g/zbdba01.dbf'有时候我们数据文件offline之后,再online需要介质恢复
SYS@orcl11g>select file#,name,status from v$datafile; FILE# NAME STATUS ---------- ------------------------------------------------------------ ------------------------------------------------------------ 1 /opt/oracle/oradata/orcl11g/system01.dbf SYSTEM 2 /opt/oracle/oradata/orcl11g/sysaux01.dbf ONLINE 3 /opt/oracle/oradata/orcl11g/undotbs01.dbf ONLINE 4 /opt/oracle/oradata/orcl11g/users01.dbf ONLINE 5 /opt/oracle/oradata/orcl11g/zbdba.dbf ONLINE 6 /opt/oracle/oradata/orcl11g/zbdba01.dbf RECOVER 7 /opt/oracle/oradata/orcl11g/test.dbf ONLINE但是我们归档已经丢失,无法完成介质恢复:
SYS@orcl11g>recover datafile 6; ORA-00279: change 1986632 generated at 10/28/2014 05:16:11 needed for thread 1 ORA-00289: suggestion : /opt/oracle/flash_recovery_area/ORCL11G/archivelog/2014_10_28/o1_mf_1_74_b4yqrglr_.arc ORA-00280: change 1986632 for thread 1 is in sequence #74 Specify log: {<RET>=suggested | filename | AUTO | CANCEL} ORA-00308: cannot open archived log '/opt/oracle/flash_recovery_area/ORCL11G/archivelog/2014_10_28/o1_mf_1_74_b4yqrglr_.arc' ORA-27037: unable to obtain file status Linux-x86_64 Error: 2: No such file or directory Additional information: 3所以这时候我们直接修改文件头进行online:
[oracle@ogg1 lib]$ bbed parfile=par.txt Password: BBED: Release 2.0.0.0.0 - Limited Production on Tue Oct 28 05:20:19 2014 Copyright (c) 1982, 2009, Oracle and/or its affiliates. All rights reserved. ************* !!! For Oracle Internal Use only !!! *************** BBED> BBED> BBED> info all File# Name Size(blks) ----- ---- ---------- 1 /opt/oracle/oradata/orcl11g/system01.dbf 0 2 /opt/oracle/oradata/orcl11g/sysaux01.dbf 0 3 /opt/oracle/oradata/orcl11g/undotbs01.dbf 0 4 /opt/oracle/oradata/orcl11g/users01.dbf 0 5 /opt/oracle/oradata/orcl11g/zbdba.dbf 0 6 /opt/oracle/oradata/orcl11g/zbdba01.dbf 0 7 /opt/oracle/oradata/orcl11g/test.dbf 0 BBED> set file 1 block 1 FILE# 1 BLOCK# 1 BBED> p kcvfhckp struct kcvfhckp, 36 bytes @484 struct kcvcpscn, 8 bytes @484 ub4 kscnbas @484 0x001e526c ub2 kscnwrp @488 0x0000 ub4 kcvcptim @492 0x3362e202 ub2 kcvcpthr @496 0x0001 union u, 12 bytes @500 struct kcvcprba, 12 bytes @500 ub4 kcrbaseq @500 0x0000004d ub4 kcrbabno @504 0x000001a6 ub2 kcrbabof @508 0x0010 ub1 kcvcpetb[0] @512 0x02 ub1 kcvcpetb[1] @513 0x00 ub1 kcvcpetb[2] @514 0x00 ub1 kcvcpetb[3] @515 0x00 ub1 kcvcpetb[4] @516 0x00 ub1 kcvcpetb[5] @517 0x00 ub1 kcvcpetb[6] @518 0x00 ub1 kcvcpetb[7] @519 0x00 BBED> p kcvfhcpc ub4 kcvfhcpc @140 0x000000f9 BBED> p kcvfhccc ub4 kcvfhccc @148 0x000000f8 BBED> set file 6 block 1 FILE# 6 BLOCK# 1 BBED> p kcvfhckp struct kcvfhckp, 36 bytes @484 struct kcvcpscn, 8 bytes @484 ub4 kscnbas @484 0x001e5048 ub2 kscnwrp @488 0x0000 ub4 kcvcptim @492 0x3362e11b ub2 kcvcpthr @496 0x0001 union u, 12 bytes @500 struct kcvcprba, 12 bytes @500 ub4 kcrbaseq @500 0x0000004a ub4 kcrbabno @504 0x00005801 ub2 kcrbabof @508 0x0010 ub1 kcvcpetb[0] @512 0x02 ub1 kcvcpetb[1] @513 0x00 ub1 kcvcpetb[2] @514 0x00 ub1 kcvcpetb[3] @515 0x00 ub1 kcvcpetb[4] @516 0x00 ub1 kcvcpetb[5] @517 0x00 ub1 kcvcpetb[6] @518 0x00 ub1 kcvcpetb[7] @519 0x00 BBED> p kcvfhcpc ub4 kcvfhcpc @140 0x0000043c BBED> p kcvfhccc ub4 kcvfhccc @148 0x0000043b BBED> modify /x 6c52 offset 484 Warning: contents of previous BIFILE will be lost. Proceed? (Y/N) y File: /opt/oracle/oradata/orcl11g/zbdba01.dbf (6) Block: 1 Offsets: 484 to 995 Dba:0x01800001 ------------------------------------------------------------------------ 6c521e00 00000000 1be16233 01000000 4a000000 01580000 10000000 02000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 0d000d00 0d000100 00000000 00000000 00000000 02008001 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 <32 bytes per line> BBED> modify /x 02e2 offset 492 File: /opt/oracle/oradata/orcl11g/zbdba01.dbf (6) Block: 1 Offsets: 492 to 1003 Dba:0x01800001 ------------------------------------------------------------------------ 02e26233 01000000 4a000000 01580000 10000000 02000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 0d000d00 0d000100 00000000 00000000 00000000 02008001 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 <32 bytes per line> BBED> modify /x f900 offset 140 File: /opt/oracle/oradata/orcl11g/zbdba01.dbf (6) Block: 1 Offsets: 140 to 651 Dba:0x01800001 ------------------------------------------------------------------------ f9000000 7fe16233 3b040000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 06000000 05005a42 44424100 00000000 00000000 00000000 00000000 00000000 00000000 06000000 00000000 00000000 a3d96233 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6b946b29 01000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6c521e00 00000000 02e26233 01000000 4a000000 01580000 10000000 02000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 0d000d00 0d000100 <32 bytes per line> BBED> modify /x f800 offset 148 File: /opt/oracle/oradata/orcl11g/zbdba01.dbf (6) Block: 1 Offsets: 148 to 659 Dba:0x01800001 ------------------------------------------------------------------------ f8000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 06000000 05005a42 44424100 00000000 00000000 00000000 00000000 00000000 00000000 06000000 00000000 00000000 a3d96233 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6b946b29 01000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 6c521e00 00000000 02e26233 01000000 4a000000 01580000 10000000 02000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 0d000d00 0d000100 00000000 00000000 <32 bytes per line> BBED> sum apply Check value for File 6, Block 1: current = 0x1924, required = 0x1924 BBED> verify DBVERIFY - Verification starting FILE = /opt/oracle/oradata/orcl11g/zbdba01.dbf BLOCK = 1 DBVERIFY - Verification complete Total Blocks Examined : 1 Total Blocks Processed (Data) : 0 Total Blocks Failing (Data) : 0 Total Blocks Processed (Index): 0 Total Blocks Failing (Index): 0 Total Blocks Empty : 0 Total Blocks Marked Corrupt : 0 Total Blocks Influx : 0 Message 531 not found; product=RDBMS; facility=BBED BBED> show all FILE# 6 BLOCK# 1 OFFSET 148 DBA 0x01800001 (25165825 6,1) FILENAME /opt/oracle/oradata/orcl11g/zbdba01.dbf BIFILE bifile.bbd LISTFILE filelist.txt BLOCKSIZE 8192 MODE Edit EDIT Unrecoverable IBASE Dec OBASE Dec WIDTH 80 COUNT 512 LOGFILE log.bbd SPOOL No BBED> p kcvfhckp struct kcvfhckp, 36 bytes @484 struct kcvcpscn, 8 bytes @484 ub4 kscnbas @484 0x001e526c ub2 kscnwrp @488 0x0000 ub4 kcvcptim @492 0x3362e202 ub2 kcvcpthr @496 0x0001 union u, 12 bytes @500 struct kcvcprba, 12 bytes @500 ub4 kcrbaseq @500 0x0000004a ub4 kcrbabno @504 0x00005801 ub2 kcrbabof @508 0x0010 ub1 kcvcpetb[0] @512 0x02 ub1 kcvcpetb[1] @513 0x00 ub1 kcvcpetb[2] @514 0x00 ub1 kcvcpetb[3] @515 0x00 ub1 kcvcpetb[4] @516 0x00 ub1 kcvcpetb[5] @517 0x00 ub1 kcvcpetb[6] @518 0x00 ub1 kcvcpetb[7] @519 0x00 BBED> p kcvfhcpc ub4 kcvfhcpc @140 0x000000f9 BBED> p kcvfhccc ub4 kcvfhccc @148 0x000000f8 BBED>修改完成后我们再次恢复该数据文件:
SYS@orcl11g>startup ORACLE instance started. Total System Global Area 417546240 bytes Fixed Size 2213936 bytes Variable Size 318769104 bytes Database Buffers 92274688 bytes Redo Buffers 4288512 bytes Database mounted. Database opened. SYS@orcl11g>recover datafile 6; Media recovery complete. SYS@orcl11g>alter database datafile 6 online; Database altered.

InnoDB使用redologs和undologs確保數據一致性和可靠性。 1.redologs記錄數據頁修改,確保崩潰恢復和事務持久性。 2.undologs記錄數據原始值,支持事務回滾和MVCC。

EXPLAIN命令的關鍵指標包括type、key、rows和Extra。 1)type反映查詢的訪問類型,值越高效率越高,如const優於ALL。 2)key顯示使用的索引,NULL表示無索引。 3)rows預估掃描行數,影響查詢性能。 4)Extra提供額外信息,如Usingfilesort提示需要優化。

Usingtemporary在MySQL查詢中表示需要創建臨時表,常見於使用DISTINCT、GROUPBY或非索引列的ORDERBY。可以通過優化索引和重寫查詢避免其出現,提升查詢性能。具體來說,Usingtemporary出現在EXPLAIN輸出中時,意味著MySQL需要創建臨時表來處理查詢。這通常發生在以下情況:1)使用DISTINCT或GROUPBY時進行去重或分組;2)ORDERBY包含非索引列時進行排序;3)使用複雜的子查詢或聯接操作。優化方法包括:1)為ORDERBY和GROUPB

MySQL/InnoDB支持四種事務隔離級別:ReadUncommitted、ReadCommitted、RepeatableRead和Serializable。 1.ReadUncommitted允許讀取未提交數據,可能導致臟讀。 2.ReadCommitted避免臟讀,但可能發生不可重複讀。 3.RepeatableRead是默認級別,避免臟讀和不可重複讀,但可能發生幻讀。 4.Serializable避免所有並發問題,但降低並發性。選擇合適的隔離級別需平衡數據一致性和性能需求。

MySQL適合Web應用和內容管理系統,因其開源、高性能和易用性而受歡迎。 1)與PostgreSQL相比,MySQL在簡單查詢和高並發讀操作上表現更好。 2)相較Oracle,MySQL因開源和低成本更受中小企業青睞。 3)對比MicrosoftSQLServer,MySQL更適合跨平台應用。 4)與MongoDB不同,MySQL更適用於結構化數據和事務處理。

MySQL索引基数对查询性能有显著影响:1.高基数索引能更有效地缩小数据范围,提高查询效率;2.低基数索引可能导致全表扫描,降低查询性能;3.在联合索引中,应将高基数列放在前面以优化查询。

MySQL學習路徑包括基礎知識、核心概念、使用示例和優化技巧。 1)了解表、行、列、SQL查詢等基礎概念。 2)學習MySQL的定義、工作原理和優勢。 3)掌握基本CRUD操作和高級用法,如索引和存儲過程。 4)熟悉常見錯誤調試和性能優化建議,如合理使用索引和優化查詢。通過這些步驟,你將全面掌握MySQL的使用和優化。

MySQL在現實世界的應用包括基礎數據庫設計和復雜查詢優化。 1)基本用法:用於存儲和管理用戶數據,如插入、查詢、更新和刪除用戶信息。 2)高級用法:處理複雜業務邏輯,如電子商務平台的訂單和庫存管理。 3)性能優化:通過合理使用索引、分區表和查詢緩存來提升性能。


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