Database Definitions (Copies/Alternatives) (ttaad4112s000)
Use this session to create copies of databases, or to create alternative databases.
Copies of databases can be created on local databases or remote databases. If a table is changed in a database the modifications are also carried out in the copy of that database. This process is called database mirroring. In case of database mirroring, only one database needs to be read. Typically, the application determines which tables have to be read. To tell the system which tables it has to read, select the Force Read check box to specify which database must be accessed to make reading tables possible.
Alternative databases are used to make sure that no data is lost when a database operation fails on the main database. From the time the database fails, data is written/retrieved of the alternative database.
Enter the code for the database and a short description. If you want to use the database on a remote system, enter the system name. Specify the database type of the local or the remote system.
If you do not fill in the System Name field, the tabledef6.X file will only be created on the local system. If this field is filled in, the database is created on the local system and on the remote system.
Make sure that the BSE_REM variable is set. You can only do this if the remote system contains the data dictionary. On the local system, the tabledef6.X file refers to the remote system. The tabledef6.X file on the remote system shows the database type per table.
If required, use variables in the Parameter field to define a database copy in another file system on your local system.
Field Information
- Database
-
The identification code of the database in the Tools environment.
- Database
-
Specifies the description of the database definition.
- Sequence No.
-
Specifies the number of the database copy. You can define more than one database definition. The database copy with the lowest number is first accessed.
- Copy/Alternative
-
Specifies whether the database is used as database copy or as an alternative database.
- System Name
-
Enter the name of the system where the database is located.
If the database is on the local system, and the system is not part of a remote database configuration, do not fill this field. Specify the database type of the local database in the Database Type field.
If you use a remote database configuration, enter the name of the system where the database is located.
Example
Assume the following configuration: host 1 : the system where the database is located workst 1: work station 1 workst 2: work station 2
The application manager works on workstation 1 and starts the Database Definitions (ttaad4110s000) session. He must enter host 1, the system where the database is located, on the System Name field. This is the system where the database is located. The application manager specifies the database type of the tables in the Database Type field. When he starts the Create Runtime Database Definitions (Tabledef) (ttaad4113s000) session the application manager can specify to dump the tabledef file on the system where the database is located, workstation 1 and workstation 2.
Note: The application manager must have a remote user file in order to have access to the systems mentioned, to dump the table definition file, tabledef, on the system host1 and workst2. - Database Type
-
Enter the database type of the database definition code. The data of those tables assigned to a database definition code, is physically stored in its database (type).
If the System Name name field is filled in, the database type of the remote system can be defined on this field. You must use this for converting data to the tabledef6.1 file on the remote system.
Tools supports several database types.
- Parameter
-
If required, enter a parameter.
If you use parameters, you can define a database copy in another file system on your local system. If the file system crashes, you still have a backup copy which is located on another file system.
The databases ORACLE and Informix use parameters, and environment variables in order to indicate tables. For example, an ORACLE database can have the following parameters: ORACLE_HOME=/usr/oracle7,ORACLE_SID=d1.
Note: It is recommended to create a database copy on a remote system. - Force to Read
-
If this check box is selected, the table is force read.
If you use more than one database, or database redirections to another system, you can specify which database must be accessed for specific tables. Typically, the bshell accesses the database that has been specified as the first database in the table's database definition.
There can be reasons, for example, performance, to read the table from another database (type). In that case, you can specify to force read table.