1.DB2實例和數據庫的目錄結構：
.1> [root@demo instance]# ./db2icrt -u fenced test
DBI1070I Program db2icrt completed successfully.
[root@demo instance]# ./db2ilist
db2inst1
test
實例test創建成功後，在實例home目錄下生成了一個sqllib文件夾/home/test/sqllib,裏面是一些配置文件以及軟鏈接
到軟件安裝目錄的文件:
[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存放目錄
-rwxr-xr-x 1 test test 6650 Dec 28 16:11 db2profile
-rw-rw-r-- 1 test test 16384 Dec 28 16:13 db2systm ---->實例配置文件get dbmcfg讀取
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 -------->系統庫目錄
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 ------>實例環境變量文件
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.
成功創建數據庫testdb後，查看數據庫的2個目錄文件：
[test@demo db2data]$ cd /db2cfg -------------->數據庫目錄
[test@demo db2cfg]$ tree
.
`-- test ------------------------------------->實例名字
`-- NODE0000 ----------------------------->節點名字
|-- SQL00001 ------------------------->數據庫編號
| |-- SQLBP.1 ---------------------->緩衝池控制文件
| |-- SQLDBCON
| |-- SQLDBCONF--------------------->數據庫參數配置文件get db cfg讀取
| |-- SQLINSLK
| |-- SQLOGCTL.LFH.2 --------------->數據庫日誌控制文件,記錄LSN可用於崩潰恢復
| |-- SQLOGDIR --------------------->數據庫日誌目錄
| | |-- S0000000.LOG
| | |-- S0000001.LOG
| | `-- S0000012.LOG
| |-- SQLOGMIR.LFH
| |-- SQLSGF.1
| |-- SQLSPCS.1 -------------------->表空間控制文件使用list tablespace
| |-- SQLTMPLK
| |-- db2event
| | `-- db2detaildeadlock
| | |-- 00000000.evt
| | `-- db2event.ctl
| |-- db2rhist.asc ------------------>數據庫歷史文件，使用list history瀏覽
| `-- db2rhist.bak
`-- sqldbdir -------------------------->本地數據庫目錄
|-- sqldbbak
|-- sqldbdir
`-- sqldbins
[test@demo TESTDB]$ cd /db2data ----------->數據庫表等對象數據存放目錄
[test@demo db2data]$ tree
.
`-- test ---------------------------------->實例名
`-- NODE0000 --------------------------->節點名
`-- TESTDB ------------------------->數據庫名字
|-- T0000000 ------------------->系統表空間,存放數據字典
| `-- C0000000.CAT
|-- T0000001 ------------------->臨時表空間，存放join排序等臨時數據
| `-- C0000000.TMP
| `-- SQLTAG.NAM
|-- T0000002 ------------------->用戶表空間，存放表索引大對象等數據
| `-- 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.系統庫目錄與本地庫目錄
[root@demo instance]# locate sqldbdir|grep test|grep -v 'dir/'
/db2cfg/test/NODE0000/sqldbdir ------>本地庫目錄，db2 list db directory on /db2cfg可見
/home/test/sqllib/sqldbdir ------->系統庫目錄，db2 list db directory可見
[test@demo NODE0000]$ db2 list db directory on /db2cfg
Local Database Directory on /db2cfg ------>本地庫目錄
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目錄損壞，上面則不能輸出數據庫信息
[test@demo ~]$ db2 list db directory
System Database Directory ------->系統庫目錄
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目錄損壞或者沒有對數據庫編目，上面則不能輸出數據庫信息，
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
重新編目數據信息，db2 list db directory則顯系統庫目錄裏有剛編目的數據庫：
[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的實例與數據庫關係
實例也叫數據庫管理器(Database Manager)，可以理解爲運行時環境包括一組進程/線程
和內存。如果數據庫是一個島嶼，實例就是通向島嶼的橋樑，刪除db2實例並不會刪除數據庫，
就是橋塌了島嶼依然在，重建實例就可以再次訪問數據庫，這與oracle數據庫非常不同，而
且db2是一個實例下可以有多個數據庫，但一個數據庫只能屬於一個實例，oracle剛好相反
一個實例只能有一個數據庫，但一個數據庫可以屬於多個實例比如RAC環境.
1>drop掉實例
[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目錄下的sqllib文件夾已經被刪除，但是並不影響
數據庫的/db2data 和 /db2cfg目錄
[test@demo ~]$ pwd
/home/test
[test@demo ~]$ ll
total 0
3>重建實例
[root@demo instance]# ./db2icrt -u fenced test
DBI1070I Program db2icrt completed successfully.
4>系統庫目錄下沒有任何數據庫
[test@demo ~]$ db2 list db directory
SQL1057W The system database directory is empty. SQLSTATE=01606
---->查看本地庫目錄卻還在
[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>編目本地數據庫
[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 ------>再次查看系統庫目錄也存在了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>連接到數據庫，可查之前插入的數據
[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