区分SID 和 GOLBAL DATABASE NAME

SID = identifies the database instance (database name + instance number). So if your database name is somedb and your instance number is 3, then your SID is somedb3.

DB Name = Name of the database (database can be shared b/t multiple instances)

DB Domain = Usually the same as your company domain (somecompany.com)

Global Database Name = Database name + database domain (somedb.somecompany.com)

Service Name = A "connector" to one or more instances. It is often useful to create additional service names in a RAC environment since the service can be modified to use particular SIDs as primary or secondary connections, or to not use certain SIDs at all.

Service Alias = An alias to the service name (just like a CNAME, etc). Say you make your service name something meaningful to the dba, but perhaps it's a bit esoteric. Create a service alias and name it something that will be meaningful to the user.

I

nstance name = same as SID