阅读背景：

透过alert日志看Oracle Startup的三个阶段

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        alert日志记载oracle实例性命周期中产生的主要事件，例如数据库启动、关闭、日志切换等，便利程序员和管理员发明问题。其中，数据库启动分为3个阶段，即nomount，mount和open。那末，在这三个阶段alert日志会记载哪些信息呢。下面我们就依照nomount，mount和open的次序逐渐启动数据库。

nomount

通过startup nomount命令将数据库启动到nomount状况，此时，数据库实例的状况是STARTED。以下所示：

点击(此处)折叠或打开

  1. SQL>
  2. SQL> startup nomount
  3. ORACLE instance started.

  5. Total System Global Area 941600768 bytes
  6. Fixed Size 1348860 bytes
  7. Variable Size 515902212 bytes
  8. Database Buffers 419430400 bytes
  9. Redo Buffers 4919296 bytes
  10. SQL>
  11. SQL> select status from v$instance;

  13. STATUS
  14. ------------
  15. STARTED

  17. SQL>
接下来，查看alert日志的输出内容以下：

点击(此处)折叠或打开

  1. Sat May 09 22:14:16 2015
  2. Starting ORACLE instance (normal)
  3. LICENSE_MAX_SESSION = 0
  4. LICENSE_SESSIONS_WARNING = 0
  5. Picked latch-free SCN scheme 2
  6. Using LOG_ARCHIVE_DEST_1 parameter default value as /u01/app/oracle/product/11.2.0/dbhome_1/dbs/arch
  7. Autotune of undo retention is turned on.
  8. IMODE=BR
  9. ILAT =27
  10. LICENSE_MAX_USERS = 0
  11. SYS auditing is disabled
  12. Starting up:
  13. Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - Production
  14. With the Partitioning, OLAP, Data Mining and Real Application Testing options.
  15. ORACLE_HOME = /u01/app/oracle/product/11.2.0/dbhome_1
  16. System name:    Linux
  17. Node name:    enmoedu1.example.com
  18. Release:    2.6.18-164.el5PAE
  19. Version:    #1 SMP Thu Sep 3 02:28:20 EDT 2009
  20. Machine:    i686
  21. VM name:    VMWare Version: 6
  22. Using parameter settings in server-side spfile /u01/app/oracle/product/11.2.0/dbhome_1/dbs/spfileHOEGH.ora
  23. System parameters with non-default values:
  24.   processes = 150
  25.   memory_target = 900M
  26.   memory_max_target = 900M
  27.   control_files = \"/u01/app/oracle/oradata/HOEGH/control01.ctl\"
  28.   control_files = \"/u01/app/oracle/oradata/HOEGH/control02.ctl\"
  29.   db_block_size = 8192
  30.   compatible = \"11.2.0.0.0\"
  31.   undo_tablespace = \"UNDOTBS1\"
  32.   remote_login_passwordfile= \"EXCLUSIVE\"
  33.   db_domain = \"\"
  34.   dispatchers = \"(PROTOCOL=TCP) (SERVICE=HOEGHXDB)\"
  35.   audit_file_dest = \"/u01/app/oracle/admin/HOEGH/adump\"
  36.   audit_trail = \"DB\"
  37.   db_name = \"HOEGH\"
  38.   open_cursors = 300
  39.   diagnostic_dest = \"/u01/app/oracle\"
  40. Sat May 09 22:14:16 2015
  41. PMON started with pid=2, OS id=5054
  42. Sat May 09 22:14:16 2015
  43. PSP0 started with pid=3, OS id=5056
  44. Sat May 09 22:14:17 2015
  45. VKTM started with pid=4, OS id=5063 at elevated priority
  46. VKTM running at (1)millisec precision with DBRM quantum (100)ms
  47. Sat May 09 22:14:17 2015
  48. GEN0 started with pid=5, OS id=5067
  49. Sat May 09 22:14:17 2015
  50. DIAG started with pid=6, OS id=5069
  51. Sat May 09 22:14:17 2015
  52. DBRM started with pid=7, OS id=5071
  53. Sat May 09 22:14:17 2015
  54. DIA0 started with pid=8, OS id=5073
  55. Sat May 09 22:14:17 2015
  56. MMAN started with pid=9, OS id=5075
  57. Sat May 09 22:14:17 2015
  58. DBW0 started with pid=10, OS id=5077
  59. Sat May 09 22:14:17 2015
  60. LGWR started with pid=11, OS id=5079
  61. Sat May 09 22:14:17 2015
  62. CKPT started with pid=12, OS id=5081
  63. Sat May 09 22:14:17 2015
  64. SMON started with pid=13, OS id=5083
  65. Sat May 09 22:14:17 2015
  66. RECO started with pid=14, OS id=5085
  67. Sat May 09 22:14:17 2015
  68. MMON started with pid=15, OS id=5087
  69. Sat May 09 22:14:17 2015
  70. MMNL started with pid=16, OS id=5089
  71. starting up 1 dispatcher(s) for network address \"(ADDRESS=(PARTIAL=YES)(PROTOCOL=TCP))\"...
  72. starting up 1 shared server(s) ...
  73. ORACLE_BASE from environment = /u01/app/oracle
由上可以看出，在nomount阶段，Oracle首先寻觅参数文件(pfile/spfile)，然后依据参数文件中的设置（如内存分配等设置），创立实例（INSTANCE），分配内存，启动后台进程。Nomount的进程也就是启动数据库实例的进程。这个进程在后台是启动Oracle可履行程序的进程，Windows上是oracle.exe文件的初始化，在Unix/Linux上是oracle可履行文件的初始化。

mount

接下来，通过alter database mount;命令将数据库启动到mount状况，此时，数据库实例的状况是MOUNTED。以下所示：

点击(此处)折叠或打开

  1. SQL>
  2. SQL> alter database mount;

  4. Database altered.

  6. SQL>
  7. SQL> select status from v$instance;

  9. STATUS
  10. ------------
  11. MOUNTED

  13. SQL>
查看alert日志的输出内容以下：

点击(此处)折叠或打开

  1. Sat May 09 22:15:30 2015
  2. alter database mount
  3. Sat May 09 22:15:34 2015
  4. Successful mount of redo thread 1, with mount id 2100626370
  5. Database mounted in Exclusive Mode
  6. Lost write protection disabled
  7. Completed: alter database mount
mount数据库的进程是读参数文件中描写的掌握文件,校验掌握文件的准确性,将掌握文件的内容读入到内存,mount是挂接的意思,是操作体系中的概念。一旦mount以后,就是将一个没成心义的实例和一个数据库产生了接洽。

open

通过alter database open;命令将数据库启动到open状况，此时，数据库实例的状况是OPEN。以下所示：

点击(此处)折叠或打开

  1. SQL>
  2. SQL> alter database open;

  4. Database altered.

  6. SQL>
  7. SQL> select status from v$instance;

  9. STATUS
  10. ------------
  11. OPEN

  13. SQL>
查看alert日志的输出内容以下：

点击(此处)折叠或打开

  1. Sat May 09 22:16:34 2015
  2. alter database open
  3. Beginning crash recovery of 1 threads
  4.  parallel recovery started with 2 processes
  5. Started redo scan
  6. Completed redo scan
  7.  read 12 KB redo, 9 data blocks need recovery
  8. Started redo application at
  9.  Thread 1: logseq 7, block 118
  10. Recovery of Online Redo Log: Thread 1 Group 1 Seq 7 Reading mem 0
  11.   Mem# 0: /u01/app/oracle/oradata/HOEGH/redo01.log
  12. Completed redo application of 0.00MB
  13. Completed crash recovery at
  14.  Thread 1: logseq 7, block 143, scn 918639
  15.  9 data blocks read, 9 data blocks written, 12 redo k-bytes read
  16. Sat May 09 22:16:34 2015
  17. Thread 1 advanced to log sequence 8 (thread open)
  18. Thread 1 opened at log sequence 8
  19.   Current log# 2 seq# 8 mem# 0: /u01/app/oracle/oradata/HOEGH/redo02.log
  20. Successful open of redo thread 1
  21. MTTR advisory is disabled because FAST_START_MTTR_TARGET is not set
  22. Sat May 09 22:16:35 2015
  23. SMON: enabling cache recovery
  24. [5095] Successfully onlined Undo Tablespace 2.
  25. Undo initialization finished serial:0 start:4294562150 end:4294562220 diff:70 (0 seconds)
  26. Verifying file header compatibility for 11g tablespace encryption..
  27. Verifying 11g file header compatibility for tablespace encryption completed
  28. SMON: enabling tx recovery
  29. Database Characterset is AL32UTF8
  30. No Resource Manager plan active
  31. replication_dependency_tracking turned off (no async multimaster replication found)
  32. Starting background process QMNC
  33. Sat May 09 22:16:35 2015
  34. QMNC started with pid=22, OS id=5274
  35. Completed: alter database open
  36. Sat May 09 22:16:36 2015
  37. Starting background process CJQ0
  38. Sat May 09 22:16:36 2015
  39. CJQ0 started with pid=24, OS id=5296
这一阶段数据库读取掌握文件中描写的数据文件并验证数据文件的一致性，如果不一致，应用日志文件将数据库文件恢复到一致的状况。数据库open后,普通用户才可以拜访数据库。

~~~~~~~ the end~~~~~~~~~
hoegh
2015.05.09
      

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