Distributed Databases
A semijoin is which of the following?

All of the attributes are sent from one site to another and then only the required rows are returned.
All of the attributes are sent from one site to another and then only the required rows are returned.
Only the joining attributes are sent from one site to another and then all of the rows are returned.
Only the joining attributes are sent from one site to another and then only the required rows are returned.

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Distributed Databases
Which of the following is true concerning a global transaction?

The required data are at one local site and the distributed DBMS routes requests as necessary.
The required data are located in at least one nonlocal site and the distributed DBMS routes requests as necessary.
The required data are located in at least one nonlocal site and the distributed DBMS passes the request to only the local DBMS.
The required data are at one local site and the distributed DBMS passes the request to only the local DBMS.

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Distributed Databases
A homogenous distributed database is which of the following?

The same DBMS is used at each location and data are distributed across all nodes.
The same DBMS is used at each location and data are not distributed across all nodes.
A different DBMS is used at each location and data are not distributed across all nodes.
A different DBMS is used at each location and data are distributed across all nodes.

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Distributed Databases
Replication should be used when which of the following exist?

When transmission speeds and capacity in a network prohibit frequent refreshing of large tables.
All of these
The application's data can be somewhat out-of-date.
When using many nodes with different operating systems and DBMSs and database designs.

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