Normal 0 7.8 磅 0 2 false false false EN-US ZH-CN X-NONEIn DB2, an instance provides an independent environment where databases can be created and

applications can be run against them. Because of these independent environments, databases in

separate instances can have the same name.

 

When DB2 is installed on the Windows platform, an instance named DB2 is created by default.

In the Linux and UNIX environments, if you choose to create the default instance, it is called

db2inst1.

 

To create an instance explicitly, use

db2icrt instance_name

To drop an instance, use

db2idrop instance_name

To start the current instance, use

db2start

To stop the current instance, use

db2stop

 

To start the DAS, use the following command:

db2admin start

To stop the DAS, use the following command:

db2admin stop

 

Like many other RDBMSs, DB2 uses different mechanisms to influence the behavior. of the

database management system. These include

• Environment variables

• DB2 profile registry variables

• Configuration parameters

Environment variables are defined at the operating system level.

set DB2INSTANCE=DB2 (on Windows)

or

export DB2INSTANCE=DB2 (on Linux and UNIX)

 

The DB2 Profile Registry is divided into four categories:

• The DB2 instance-level profile registry

• The DB2 global-level profile registry

• The DB2 instance node-level profile registry

• The DB2 instance profile registry

 

db2set -lr

To set the value of a specific variable (in this example, DB2INSTPROF) at the global level, use

db2set DB2INSTPROF="C:\PROGRAM FILES\SQLLIB" -g

To set a variable at the instance level for instance myinst, use

db2set DB2INSTPROF="C:\MY FILES\SQLLIB" -i myinst

 

Configuration parameters are defined at two different levels: the instance level and the database

level. The variables at each level are different (not like DB2 registry variables, where the same

variables can be defined at different levels).

To view the contents of the Database Manager Configuration file, issue the command:

db2 get dbm cfg

To update the value of a specific parameter, use

db2 update dbm cfg using parameter value

For example

db2 update dbm cfg using INTRA_PARALLEL YES

 

To view the contents of the Database Configuration file, issue the command:

db2 get db cfg for dbname

For example

db2 get db cfg for mydb2

To update the value of a specific variable, use

db2 update db cfg for dbname using parameter value

For example

db2 update db cfg for mydb2 using MINCOMMIT 3

 

In DB2, directories are used to store connectivity information about databases and the servers on

which they reside.

1.         System Database Directory

The system database directory (or system db directory) is like the main “table of contents” that  contains information about all the databases to which you can connect from your DB2 server.

 

To list the contents of the system db directory, use the command:

db2 list db directory

 

To list the contents of the system db directory, use the command:

db2 list db directory

Any entry from the output of this command containing the word Indirect indicates that the entry

is for a local database, that is, a database that resides on the data server on which you are working.

The entry also points to the local database directory indicated by the Database drive item

(Windows) or Local database directory (Linux or UNIX).

Any entry containing the word Remote indicates that the entry is for a remote database—a

database residing on a server other than the one on which you are currently working. The entry

also points to the node directory entry indicated by the Node name item.

To enter information into the system database directory, use the catalog command:

db2 catalog db dbname as alias at node nodename

For example

db2 catalog db mydb as yourdb at node mynode

The catalog commands are normally used only when adding information for remote databases.

For local databases, a catalog entry is automatically created after creating the database

with the CREATE DATABASE command.

2.         Local Database Directory

The local database directory contains information about databases residing on the server where  you are currently working.

To list the contents of the local database directory, issue the command:

db2 list db directory on drive / path

3.         Node Directory

The node directory stores all connectivity information for remote database servers

To list the contents of the node directory, issue the command:

db2 list node directory

To enter information into the node directory, use

db2 catalog tcpip node node_name

remote hostname or IP_address

server service_name or port_number

For example

db2 catalog tcpip node mynode

remote 192.168.1.100

server 60000

 

4.         Database Connection Services Directory

The Database Connection Services (DCS) directory contains connectivity information for host  databases residing on System z (z/OS or OS/390) or System i (OS/400) server. You need to have  DB2 Connect software installed.

 

To list the contents of the DCS directory, issue the following command:

db2 list dcs directory

To enter information into the DCS directory, use

db2 catalog dcs db dbname as location_name

For example

db2 catalog dcs db mydb as db1g

 

Three table spaces—SYSCATSPACE (holding the Catalog tables), TEMPSPACE1 (system temporary

space), and USERSPACE1 (the default user table space)—are automatically created

when you create a database. SYSCATSPACE and TEMPSPACE1 can be considered system

structures, as they are needed for the normal operation of your database. SYSCATSPACE contains

the catalog tables containing metadata (data about your database objects) and must exist at

all times. Some other RDBMSs call this structure a “data dictionary.”

 

If the database you want to access is MYDB2, which was in the myinst instance, you would first

need to create this instance, switch to the instance, and then issue the catalog command as

shown below.

db2icrt myinst

set DB2INSTANCE=myinst

catalog db mydb2 on h:

It is a good practice to back up the contents of all your configuration files as shown below.

db2 get dbm cfg > dbmcfg.bk

db2 get db cfg for database_name > dbcfg.bk

db2set -all > db2set.bk

db2 list db directory > systemdbdir.bk

db2 list node directory > nodedir.bk

db2 list dcs directory > dcsdir.bk

 

Database federated support in DB2 allows tables from multiple databases to be presented as

local tables to a DB2 server. The databases may be local or remote; they can also belong to different

RDBMSs.

 

First of all, make sure that your server allows federated support: The database manager parameter

FEDERATED must be set to YES.