This section describes two examples of the parametrization of SESDCN by means of control statements. In the first, the communication between application programs and DBHs is to be implemented for local access, whereas in the second, it is to be implemented for remote access as well. The control statements for parametrizing SESDCN are stored in an input file that must be assigned before SESDCN is started.
Local access
In distributed processing with SESAM/SQL-DCN, application programs can communicate with more than one DBH. If the application program and database belong to the same configuration, we talk about local access (see the “ Core manual”).
The figure 2 shows a simple example of local access. The two loaded DBHs on processor P412 with their assigned databases belong to configuration S. To enable application programs belonging to this configuration to access the databases via these two DBHs, the SESDCN distribution component with the DCN name R and the configuration name S is loaded.
Figure 2: Example of a distributed application with local access
The input file for the control statements of the SESDCNR distribution component contains the following:
//SET-DCN-OPTIONS - // DCN-IDENTIFICATION=*PARAMETERS - // (CONFIGURATION-NAME=S,DCN-NAME=R) //ADD-DISTRIBUTION-RULE-LIST - // CATALOG-NAME-1=COMPANY(LINK-NAME=*HOME,DBH-NAME=A), - // CATALOG-NAME-2=STAFF(LINK-NAME=*HOME,DBH-NAME=B) //END
An ADD-NETWORK-LINK-LIST statement is not necessary, since all the databases entered in the distribution rule are assigned to the same configuration.
Remote access
In distributed processing, if application programs access databases in other configurations, we talk about remote access. Remote access can take place on a single computer or across computer boundaries.
The figure 3 shows a simple example of a distributed application with remote access. An SESDCN and a DBH are loaded in configuration A on processor P614. Processor P616 contains two configurations (B and C), each with an SESDCN and a DBH. Application programs are to be able to access all databases in the network.
The names of the configurations are unique throughout the network so that, in the event of a computer failure, a restart is possible on the other computer at any time (see section “Restarting an SESDCN session”).
For the sake of clarity, only the access paths going from configuration A to configurations B and C are shown in the following figure.
Figure 3: Example of a distributed application with remote access
The input file for the control statements of the SESDCNA distribution component contains the following:
//SET-DCN-OPTIONS - // DCN-IDENTIFICATION=*PARAMETERS - // (CONFIGURATION-NAME=A,DCN-NAME=A)- //ADD-DISTRIBUTION-RULE-LIST - // CATALOG-NAME-1=WAREHOUSE1(LINK-NAME=*HOME,DBH-NAME=3), - // CATALOG-NAME-2=WAREHOUSE2(LINK-NAME=*HOME,DBH-NAME=3), - // CATALOG-NAME-3=CUSTOMERS(LINK-NAME=PARTNER1,DBH-NAME=4), - // CATALOG-NAME-4=SALES(LINK-NAME=PARTNER2,DBH-NAME=5) //ADD-NETWORK-LINK-LIST - // LINK-NAME1=PARTNER1(PROCESSOR-NAME=P616, - // CONFIGURATION-NAME=B, - // DCN-NAME=X), - // LINK-NAME2=PARTNER2(PROCESSOR-NAME=P616, - // CONFIGURATION-NAME=C, - // DCN-NAME=Y) //END
The input file for the control statements of the SESDCNX distribution component contains the following:
//SET-DCN-OPTIONS - // DCN-IDENTIFICATION=*PARAMETERS - // (CONFIGURATION-NAME=B,DCN-NAME=X) //ADD-DISTRIBUTION-RULE-LIST - // CATALOG-NAME-1=WAREHOUSE1(LINK-NAME=PARTNER2,DBH-NAME=3), - // CATALOG-NAME-2=WAREHOUSE2(LINK-NAME=PARTNER2,DBH-NAME=3), - // CATALOG-NAME-3=CUSTOMERS(LINK-NAME=*HOME,DBH-NAME=4), - // CATALOG-NAME-4=SALES(LINK-NAME=PARTNER1,DBH-NAME=5) //ADD-NETWORK-LINK-LIST // LINK-NAME1=PARTNER1(PROCESSOR-NAME=P616, - // CONFIGURATION-NAME=C, - // DCN-NAME=Y), - // LINK-NAME2=PARTNER2(PROCESSOR-NAME=P614, - // CONFIGURATION-NAME=A, - // DCN-NAME=A) //END
the following:
//SET-DCN-OPTIONS - // DCN-IDENTIFICATION=*PARAMETERS - // (CONFIGURATION-NAME=C,DCN-NAME=Y) //ADD-DISTRIBUTION-RULE-LIST - // CATALOG-NAME-1=WAREHOUSE1(LINK-NAME=PARTNER2,DBH-NAME=3), - // CATALOG-NAME-2=WAREHOUSE2(LINK-NAME=PARTNER2,DBH-NAME=3), - // CATALOG-NAME-3=CUSTOMERS(LINK-NAME=PARTNER1,DBH-NAME=4), - // CATALOG-NAME-4=SALES(LINK-NAME=*HOME,DBH-NAME=5) //ADD-NETWORK-LINK-LIST // LINK-NAME1=PARTNER1(PROCESSOR-NAME=P616, - // CONFIGURATION-NAME=B, - // DCN-NAME=X), - // LINK-NAME2=PARTNER2(PROCESSOR-NAME=P614, - // CONFIGURATION-NAME=A, - // DCN-NAME=A) //END