Oracle Network Administration (1 of 3)

  1. Networking Overview

    1. Identify networking business trends

      2. Is it necessary to illustrate ? In a Nutshell:Client-Server

    2. Describe Oracle networking solutions

      3. Oracle networking environments are based on two concepts:

      Distributed Processing: Client and servers exist as separate logical entities on separate physical machines. This configuration allows for the division of labor where resources are allocated efficiently between a client workstation and the server machine.

      Stack Communications: The concept of distributed processing relies on the ability of computers separated by both design and physical location to communicate and interact with each other. This is accomplished through a process known as stack communications. The layers in a typical Oracle communications stack are similar to those of a standard OSI communications stack

      In an Oracle client-server transaction, information passes through the following layers:

        1. Client Application: Provide all user-orientated activities, such as character or graphical user display, screen control, data presentation, application flow, and other application specifics. The application identifies database operations to send the server and passes them through the Oracle Call Interface (OCI).
        2. Oracle Call Interfaca (OCI): The OCI code contains all the information required to initiate a SQL dialogue between the client and the server. It defines calls to the server to: parse SQL statements for syntax validations, open a cursor for the SQL statement, bind client application variables into the server shared memory, describe the contents of the fields being returned based on the values in the servers data dictionary, execute SQL statements within the cursor memory space,fetch one or more rows of data into the client application,close the cursor.

          3. The client application uses a combination of these calls to request activity within the server. OCI calls can be combined into a single message to the server, or they may be processed one at a time through multiple messages to the server, depending on the nature of the client application. Oracle products attempt to minimize the number of messages sent to the server be combining many OCI calls into a single message to the server. When a call is performed, control is passed to Net8 to establish the connection and transmit the request to the server.

        1. Two Task Common : Provides character set and data type conversion between different character sets or formats on the client and the server. This layer is optimized to perform conversion only when required on a per connection basis. At the time of connection, it is reponsible for evaluating differences in internal data and charactet set representations and determining wheter conversions are required for the two computers to communicate.
        2. Net8 : Provides all session layer functionality in an Oracle communications stack. It is responsible for establishing and maintaining the connection between a client application and a server, as well as exchanging massages between them. Net8 itself has three component layers that facilitate session layer functionality :
            1. Network Interface (NI)- This layer provides a generic interface for Oracle clients, servers, or external processes to access Net8 functions. The NI handles the "break" and "reset" requests for a connection.
            2. Network Routing (NR)/Network Naming(NN)/Network Authentication(NA) - NR provides routing of the session to the destination. This may include any intermediary destination or 'hops', on the route to the server destination. NN resolves aliases to a Net8 destination address. NA negotiates any authentication requirement with the destination.
            3. Transparent Network Substrat (TNS)- TNS is an underlying layer of Net8 providing a common interface to industry standard protocols. TNS receives requests from Net8, and settlles all generic machine-level connectivity issues, such as: the location of the server or destination ( open, close functions); wheter one or more protocols will be involved in the connection ( open,close functions); and how to handle interrupts between client and server based on the capabilities of each ( send, receive functions). The generic set of TNS functions ( open , close, send, receive) passes control to an Oracle Protocol Adapter to make a protocol-specific call. Additionally, TNS supports encryption and sequenced cryptographic message digests to protect data in transit.
        3. Oracle Protocol Adapters : Are responsible for mapping TNS functionality to industry-standard protocols used in the client-server connection. Each adapter is responible for mapping the equivalent functions between TNS and specific protocol
        4. Network Specific Protocols: All Oracle client-server connection require an existing network protocol stack to make the machine-level connection between the two machines. The network protocol is responsible only for getting the data from the client machine to the server machine, at which point the data is passed to the server-side Oracle Protocol Adapter
        5. Server side Interaction : The following components above the Net8 session layer are different from those on the client side:
        6. Oracle Program Interface (OPI) : It performs a complementary function to that of the OCI. It is reponsible for responding to each of the possible messages sent by the OCI.e.g., an OCI request to fetch 25 rows would have an OPI reponse to return the 25 rows once they have been fetched.
        7. Oracle Server : The Oracle Server side of the connection is responsible for receiving dialog requests from the client OCI code and resolving SQL statments on behalf of the client application. Once received, a request is processed and the resulting data is passed to the OPI for responses to be formatted and returned to the client applciation.
        8. Server to Server Interaction : When two servers communicate to complete a distributed transaction, the process, layers, and dialogues are the same as in the client-server scenarion, except that there is no client application. The server has its own version of OCI, called the Network Program Interface (NPI). The NPI interface performs all of the functions that the OCI does for clients, allowing a coordinating server to contruct SQL requests for additional servers.