DB2实例与数据库关系及目录结构

1.DB2实例和数据库的目录结构：

.1> [root@demo instance]# ./db2icrt -u fenced test
      DBI1070I  Program db2icrt completed successfully.
      [root@demo instance]# ./db2ilist
      db2inst1
      test

实例test创建成功后，在实例home目录下生成了一个sqllib文件夹/home/test/sqllib,里面是一些配置文件以及软链接

到软件安装目录的文件:

[test@demo sqllib]$ ll
total 92
drwxr-xr-x 2 test test  4096 Dec 28 16:11 adm
lrwxrwxrwx 1 root test    22 Dec 28 16:11 adsm -> /opt/ibm/db2/V9.7/adsm
drwxr-x--- 2 test test  4096 Dec 28 16:11 backup
lrwxrwxrwx 1 root test    21 Dec 28 16:11 bin -> /opt/ibm/db2/V9.7/bin
drwxrwsr-t 2 test test  4096 Dec 28 16:13 cfg
lrwxrwxrwx 1 root test    22 Dec 28 16:11 conv -> /opt/ibm/db2/V9.7/conv
-rwxr-xr-x 1 test test 10575 Dec 28 16:11 db2cshrc
drwxrwsrwt 4 test test  4096 Dec 28 16:18 db2dump ------->db2diag.log存放目录
-rwxr-xr-x 1 test test  6650 Dec 28 16:11 db2profile
-rw-rw-r-- 1 test test 16384 Dec 28 16:13 db2systm   ---->实例配置文件get dbmcfg读取
lrwxrwxrwx 1 root test    21 Dec 28 16:11 doc -> /opt/ibm/db2/V9.7/doc
drwxrwsr-t 4 test test  4096 Dec 28 16:11 function
lrwxrwxrwx 1 root test    23 Dec 28 16:11 gskit -> /opt/ibm/db2/V9.7/gskit
drwx------ 3 test test  4096 Dec 28 16:13 hmonCache
lrwxrwxrwx 1 root test    22 Dec 28 16:11 java -> /opt/ibm/db2/V9.7/java
lrwxrwxrwx 1 root test     5 Dec 28 16:11 lib -> lib32
lrwxrwxrwx 1 root test    23 Dec 28 16:11 lib32 -> /opt/ibm/db2/V9.7/lib32
drwxrwsr-t 2 test test  4096 Dec 28 16:11 log
lrwxrwxrwx 1 root test    22 Dec 28 16:11 misc -> /opt/ibm/db2/V9.7/misc
lrwxrwxrwx 1 root test    25 Dec 28 16:11 samples -> /opt/ibm/db2/V9.7/samples
drwxr-xr-x 3 test test  4096 Dec 28 16:11 security
drwxr-xr-x 3 test test  4096 Dec 28 16:11 security32
drwxrwxr-x 2 test test  4096 Dec 28 16:12 sqldbdir  -------->系统库目录
drwxrwsrwx 2 test test  4096 Dec 28 16:11 tmp
lrwxrwxrwx 1 root test    23 Dec 28 16:11 tools -> /opt/ibm/db2/V9.7/tools
drwxrwxrwx 2 test test  4096 Dec 28 16:13 uif
-rwxr-xr-x 1 test test     0 Dec 28 16:11 usercshrc
-rwxr-xr-x 1 test test     0 Dec 28 16:11 userprofile ------>实例环境变量文件

2>[test@demo ~]$ db2start
SQL1063N  DB2START processing was successful.
[test@demo ~]$ db2 create db testdb on /db2data dbpath on /db2cfg
DB20000I  The CREATE DATABASE command completed successfully.

成功创建数据库testdb后，查看数据库的2个目录文件：

[test@demo db2data]$ cd /db2cfg -------------->数据库目录
[test@demo db2cfg]$ tree
.
`-- test ------------------------------------->实例名字
    `-- NODE0000 ----------------------------->节点名字
        |-- SQL00001 ------------------------->数据库编号
        |   |-- SQLBP.1 ---------------------->缓冲池控制文件
        |   |-- SQLDBCON
        |   |-- SQLDBCONF--------------------->数据库参数配置文件get db cfg读取
        |   |-- SQLINSLK
        |   |-- SQLOGCTL.LFH.2 --------------->数据库日志控制文件,记录LSN可用于崩溃恢复
        |   |-- SQLOGDIR --------------------->数据库日志目录
        |   |   |-- S0000000.LOG
        |   |   |-- S0000001.LOG
        |   |   `-- S0000012.LOG
        |   |-- SQLOGMIR.LFH 
        |   |-- SQLSGF.1
        |   |-- SQLSPCS.1 -------------------->表空间控制文件使用list tablespace
        |   |-- SQLTMPLK
        |   |-- db2event
        |   |   `-- db2detaildeadlock
        |   |       |-- 00000000.evt
        |   |       `-- db2event.ctl
        |   |-- db2rhist.asc ------------------>数据库历史文件，使用list history浏览
        |   `-- db2rhist.bak
        `-- sqldbdir -------------------------->本地数据库目录
            |-- sqldbbak
            |-- sqldbdir
            `-- sqldbins

[test@demo TESTDB]$ cd /db2data  ----------->数据库表等对象数据存放目录
[test@demo db2data]$ tree
.
`-- test  ---------------------------------->实例名
    `-- NODE0000 --------------------------->节点名
        `-- TESTDB ------------------------->数据库名字
            |-- T0000000 ------------------->系统表空间,存放数据字典
            |   `-- C0000000.CAT
            |-- T0000001 ------------------->临时表空间，存放join排序等临时数据
            |   `-- C0000000.TMP
            |       `-- SQLTAG.NAM
            |-- T0000002 ------------------->用户表空间，存放表索引大对象等数据
            |   `-- C0000000.LRG
            `-- T0000003
                `-- C0000000.LRG


[test@demo ~]$ db2 list tablespace containers for 1 show detail

            Tablespace Containers for Tablespace 1

 Container ID                         = 0
 Name                                 = /db2data/test/NODE0000/TESTDB/T0000001/C0000000.TMP
 Type                                 = Path
 Total pages                          = 1
 Useable pages                        = 1
 Accessible                           = Yes

2.系统库目录与本地库目录

[root@demo instance]# locate sqldbdir|grep test|grep -v 'dir/'
/db2cfg/test/NODE0000/sqldbdir ------>本地库目录，db2 list db directory on /db2cfg可见
/home/test/sqllib/sqldbdir             ------->系统库目录，db2 list db directory可见

[test@demo NODE0000]$ db2 list db directory on /db2cfg 

 Local Database Directory on /db2cfg   ------>本地库目录
 Number of entries in the directory = 1
Database 1 entry:

 Database alias                       = TESTDB
 Database name                        = TESTDB
 Database directory                   = SQL00001
 Database release level               = d.00
 Comment                              =
 Directory entry type                 = Home
 Catalog database partition number    = 0
 Database partition number            = 0

如果/db2cfg/test/NODE0000/sqldbdir目录损坏，上面则不能输出数据库信息



[test@demo ~]$ db2 list db directory
 
System Database Directory     ------->系统库目录
 Number of entries in the directory = 1
Database 1 entry:

 Database alias                       = TESTDB
 Database name                        = TESTDB
 Local database directory             = /db2cfg
 Database release level               = d.00
 Comment                              =
 Directory entry type                 = Indirect
 Catalog database partition number    = 0
 Alternate server hostname            =
 Alternate server port number         =

如果/home/test/sqllib/sqldbdir目录损坏或者没有对数据库编目，上面则不能输出数据库信息，
也就不能db2 connect to db了，如下：

[test@demo NODE0000]$ db2 uncatalog database testdb
DB20000I  The UNCATALOG DATABASE command completed successfully.
DB21056W  Directory changes may not be effective until the directory cache is 
refreshed.

[test@demo NODE0000]$ db2 list db directory
SQL1057W  The system database directory is empty.  SQLSTATE=01606

重新编目数据信息，db2 list db directory则显系统库目录里有刚编目的数据库：
[test@demo ~]$ db2 catalog database testdb on /db2cfg
DB20000I  The CATALOG DATABASE command completed successfully.
DB21056W  Directory changes may not be effective until the directory cache is 
refreshed.

[test@demo ~]$ db2 list db directory

 System Database Directory
 Number of entries in the directory = 1
 Database alias                       = TESTDB
 Database name                        = TESTDB
 Local database directory             = /db2cfg

3.DB2的实例与数据库关系

实例也叫数据库管理器(Database Manager)，可以理解为运行时环境包括一组进程/线程
和内存。如果数据库是一个岛屿，实例就是通向岛屿的桥梁，删除db2实例并不会删除数据库，
就是桥塌了岛屿依然在，重建实例就可以再次访问数据库，这与oracle数据库非常不同，而
且db2是一个实例下可以有多个数据库，但一个数据库只能属于一个实例，oracle刚好相反
一个实例只能有一个数据库，但一个数据库可以属于多个实例比如RAC环境.

1>drop掉实例
[root@demo instance]# pwd
/opt/ibm/db2/V9.7/instance
[root@demo instance]# ./db2idrop test
DBI1070I  Program db2idrop completed successfully.

[root@demo instance]# ./db2ilist
 db2inst1

2>查看test的home目录下的sqllib文件夹已经被删除，但是并不影响
  数据库的/db2data 和 /db2cfg目录
[test@demo ~]$ pwd
/home/test
[test@demo ~]$ ll
total 0

3>重建实例
[root@demo instance]# ./db2icrt -u fenced test
   DBI1070I  Program db2icrt completed successfully.

4>系统库目录下没有任何数据库
[test@demo ~]$ db2 list db directory
SQL1057W  The system database directory is empty.  SQLSTATE=01606

---->查看本地库目录却还在
[test@demo ~]$ db2 list db directory on /db2cfg  
 Local Database Directory on /db2cfg
 Number of entries in the directory = 1
Database 1 entry:

 Database alias                       = TESTDB
 Database name                        = TESTDB
 Database directory                   = SQL00001
 Database release level               = d.00
 Comment                              =
 Directory entry type                 = Home

5>编目本地数据库
[test@demo ~]$ db2 catalog database testdb on /db2cfg
DB20000I  The CATALOG DATABASE command completed successfully.
DB21056W  Directory changes may not be effective until the directory cache is 
refreshed.
[test@demo ~]$ db2 list db directory

 System Database Directory      ------>再次查看系统库目录也存在了testdb
 Number of entries in the directory = 1
Database 1 entry:

 Database alias                       = TESTDB
 Database name                        = TESTDB
 Local database directory             = /db2cfg
 Database release level               = d.00
 Comment                              =
 Directory entry type                 = Indirect
 Catalog database partition number    = 0
 Alternate server hostname            =
 Alternate server port number         =

6>连接到数据库，可查之前插入的数据
[test@demo ~]$ db2start
SQL1063N  DB2START processing was successful.
[test@demo ~]$ db2 connect to testdb

   Database Connection Information

 Database server        = DB2/LINUX 9.7.2
 SQL authorization ID   = TEST
 Local database alias   = TESTDB

[test@demo ~]$ db2 "select * from tb1"

ID          NAME      
----------- ----------
          1 yo1       
          2 yo2