Can DHCP computers serve as database server?

Question

My laptop is a DHCP computer. I installed Loopback adapter for Oracle 10g Release 2. Can it serve as a database server? Can I use other computer with the client installation to access to the database server? Or I must install the client software at the laptop with the server installation. In this case, does the client connects to the server using Oracle Net Services?
Thanks.

Answer 1

Two parts here: DHCP and Database access.
1) DHCP
This is for finding/identifying the computer and is not part of the database discussion. (Assuming TCP/IP for this discussion ...)
A computer has an address and a name. The address is an IP address which may be 'statically' or 'dynamically' assigned. If static, a network admin provides the P address. If dynamc, it is assigned using DHCP. The name is just a readable alias for the address and tat is stored in either a lookup file (/etc/hosts) or 'resolved' by a program called DNS.
The problem with DHCP is that the computer name and address are provided on a time-limited lease. This means that the address can change over time.
A server should be at a known address so that clients can find it easily. (Imagine if your favorite grocery store moved every few weeks.)
So, while a server can use DHCP to run it's service, there is a risk that the service could become unavailable due to retrained leased. To mitigate that risk requires the network administration to take even further steps, such as Dynamic DNS.
Oracle 11gR2 is looking at mitigating that issue to some extent using a 'GNS server'.
2) Database access
The other part to your question relates to the 'service' and/or 'sid'. In brief:
- A sid represents the physical database instance (and is used to derive the start of memory for the database instance)
- A service is logical and points to one or more SIDs (in RAC or standby, the service can imply multiple instances)
- A database instance has at least one service and that service matches the sid
- A database instance may support other services
- A database instance registers the services that it will honour with the listener
- The listener will listen on a network for 'requests for a service'
A TCP/IP client will always use a 3-part request to get to the database instance. The 3 parts are "host computer where the listener is", "the port on which to connect to the listener" "the service for which the listener should provide the final connection". Some of these parts may be implied, but in TCP/IP they are always there.
When you connect using a non-Java client, you may see a connection request like
sqlplus user/password@alias
and the alias looks up in some 'resolver mechanism' to translate the alias into the 3 parts. The resolver mechanism is often the TNSNAMES.ORA usually installed with the client, although that could be different based on the contents of the SQLNET.ORA
In a Java (JDBC) connect, you will use a URL like "jdbc:oracle:thin:scott/tiger@//myhost:1521/orcl" - which is basically "jdbc:oracle:thin:user/password@//host:port/service" (see http://www.oracle.com/technology/tech/java/sqlj_jdbc/htdocs/jdbc_faq.html)
The HOST part in the above needs to get translated into a specific computer - and that is the link back to hostname, IP address, DHCP and DNS.
HTH
/Hans