前言
当Oracle 归档日志满了后，将无法正常登入oracle，需要删除一部分归档日志才能正常登入ORACLE。最近同事在工作中遇到一个问题，他那边的一套Oracle 11g数据库使用RMAN没办法删除旧的归档，导致磁盘使用率很高。
1.查看归档日志文件
oracle@ps251n2s:[/opt/oracle/archive/db] ls -ltr |more
total 3059881082
-rw-r----- 1 oracle oinstall 725320704 May 20 2016 1_1_91233774.dbf
-rw-rw---- 1 oracle oinstall 1756937216 Jun 7 2016 1_2_91233774.dbf
-rw-rw---- 1 oracle oinstall 1756731392 Jun 21 2016 1_3_91233774.dbf
-rw-rw---- 1 oracle oinstall 1758001152 Jul 3 2016 1_4_91233774.dbf
-rw-rw---- 1 oracle oinstall 1756729344 Jul 15 2016 1_5_91233774.dbf
-rw-rw---- 1 oracle oinstall 1765750784 Jul 26 22:00 1_6_91233774.dbf
-rw-rw---- 1 oracle oinstall 1760346112 Aug 6 14:04 1_7_91233774.dbf
......
2.使用 RMAN list archivelog all; 查看日志也没有显示旧归档日志的记录
RMAN> list archivelog all;
using target database control file instead of recovery catalog
List of Archived Log Copies for database with db_unique_name DBS
=====================================================================
Key Thrd Seq S Low Time
------- ---- ------- - ---------
1206 1 1206 A 14-JAN-17
Name: opt/oracle/archive/db/1_1206_91233774.dbf
1207 1 1207 A 14-JAN-17
Name: opt/oracle/archive/db/1_1207_91233774.dbf
1208 1 1208 A 14-JAN-17
Name: opt/oracle/archive/db/1_1208_91233774.dbf
......
3.使用crosscheck检查也没有查到旧归档日志记录
RMAN> crosscheck archivelog all;
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=16 device type=DISK
validation succeeded for archived log
archived log file name=/opt/oracle/archive/db/1_1206_91233774.dbf RECID=1206 STAMP=933244655
validation succeeded for archived log
archived log file name=/opt/oracle/archive/db/1_1207_91233774.dbf RECID=1207 STAMP=933249510
validation succeeded for archived log
archived log file name=/opt/oracle/archive/db/1_1208_91233774.dbf RECID=1208 STAMP=933254500
validation succeeded for archived log
archived log file name=/opt/oracle/archive/db/1_1209_91233774.dbf RECID=1209 STAMP=933259445
validation succeeded for archived log
4.查看v$archived_log视图也没有旧归档日志记录
解决过程
1.在网上找到一篇文章，大体意思是MAN删除归档日志的依据是controlfile中记录的归档日志，而不是你磁盘上实际存在的归档日志，如果你的归档日志已经不在controlfile中就无法被RMAN识别到，也就无法被删除。而致于归档信息何时在控制文件中被覆盖，这由一个参数control_file_record_keep_time来控制。
查看数据库中的参数是默认的7天
SYS@db> show parameter CONTROL_FILE_RECORD_KEEP_TIME
NAME TYPE VALUE
------------------------------------ -------------------------------- ------------------------------
control_file_record_keep_time integer 7
2.难道是在控制文件中归档日志的记录条数只能保留7天的么？于是到MOS去找相关文档找到一篇Why Are Controlfile Entries For Archived Logs Not Overwritten After CONTROL_FILE_RECORD_KEEP_TIME? (文档 ID 1056085.1)，文档介绍CONTROL_FILE_RECORD_KEEP_TIME参数并不是强制在控制文件中保留多少天的归档日志条目，而是由V$CONTROLFILE_RECORD_SECTION视图中的ARCHIVED LOG条目去控制的，当RECORDS_TOTAL=RECORDS_USED时旧的归档日志就会被覆盖掉。
于是查数据库中的V$CONTROLFILE_RECORD_SECTION视图，看到ARCHIVED LOG行的records_total=224意味着控制文件中只能保留224条归档日志文件信息。
SYS@dbs> select * from v$controlfile_record_section where type='ARCHIVED LOG';
TYPE RECORD_SIZE RECORDS_TOTAL RECORDS_USED FIRST_INDEX LAST_INDEX LAST_RECID
---------------------------- ----------- ------------- ------------ ----------- ---------- ----------
ARCHIVED LOG 584 224 224 88 87 1235
3.查询v$archived_log视图，总数为224条
SYS@dbs> select count(*) from v$archived_log;
COUNT(*)
----------
224
4.这时应该可以推断出由于控制文件中只能保留224条归档日志数据，所以以前的归档信息已经被控制文件刷出，RMAN无法识别到这些归档文件，所以就无法删除这些归档日志。
5.那么现在如果使用RMAN删除这些旧的归档日志呢？我想到使用 catalog start with 命令重新注册这些文件到控制文件中
RMAN> catalog start with '/opt/oracle/archive/db';
......
File Name: /opt/oracle/archive/db/1_1005_91233774.dbf
File Name: /opt/oracle/archive/db/1_1006_91233774.dbf
File Name: /opt/oracle/archive/db/1_1007_91233774.dbf
Do you really want to catalog the above files (enter YES or NO)? yes
cataloging files...
cataloging done
......
RMAN> list archivelog all;
.....
1236 1 301 A 22-OCT-16
Name: /opt/oracle/archive/db/1_301_91233774.dbf
1237 1 302 A 22-OCT-16
Name: /opt/oracle/archive/db/1_302_91233774.dbf
......
6.旧的归档日志文件已经注册到控制文件中了，再使用RMAN进行删除就可以了
delete archivelog until logseq 1007;
7.再次查询v$controlfile_record_section视图，records_total也被“撑”大了
SYS@db> select * from v$controlfile_record_section where type='ARCHIVED LOG';
TYPE RECORD_SIZE RECORDS_TOTAL RECORDS_USED FIRST_INDEX LAST_INDEX LAST_RECID
---------------------------- ----------- ------------- ------------ ----------- ---------- ----------
ARCHIVED LOG 584 896 742 807 652 1800
至此问题结束。
