Dependencies between resources

TADDM discovers and categorizes several types of cross-tier dependencies, these dependencies are reflected in the CDM. Dependencies model the runtime relationships among the various components within the CDM.

There are several types of dependencies, including:

  • Transactional dependencies

    Transactional dependencies occur between application components, such as web servers, application servers, and databases. The dependent component issues requests to the provider component in order to perform certain functions. For example, a Java™ Database Connectivity (JDBC) connection from a Java 2 Platform, Enterprise Edition (Java EE) server to a database is a transactional dependency. In this case, the provider is often called a server and the dependent called a consumer or client.

  • Service dependencies

    Service dependencies occur between application components and infrastructure services, such as Domain Name System (DNS), Lightweight Directory Access Protocol (LDAP), and Network File System (NFS). The provider is the infrastructure service, and the dependent component requests system services from the provider. For example, a request to map a DNS name to an IP address.

  • IP dependencies

    IP dependencies occur between two computer systems or between an application server and a computer system. TADDM creates this type of relationship when it discovers a relationship between two computer systems but cannot discover exactly which application server is involved.

  • System dependencies

    System dependencies occur between an application server and its host computer system.

  • Application to application dependencies

    Application to application dependencies occur from one business application to another business application.

Example of dependencies

When transaction dependencies are created for two application servers, then IP dependencies are not created between them. Neither are IP dependencies created between the application server and their hosts. However, there can exist another logical connection for example between two processes and based on these connections IP dependencies can be created between computer systems. For example, consider the following scenario:
  • Computer system (CS1) hosts an application server (AP1) and process (P1)
  • Computer system (CS2) hosts an application server (AP2) and process (P2)

    There are two logical connections created by TADDM: AP1 <-> AP2 and P1<->P2

In this scenario, a transactional dependence is created between AP1 and AP2 (based on the logical connection AP1 <-> AP2). An IP dependency is created between CS1 and CS2 (based on the logical connection between P1<->P2).