NonStop Systems Introduction for H-Series RVUs

Integrity NonStop NS-Series Server Architecture
NonStop Systems Introduction for H-Series RVUs—540083-001
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Easy Expansion of Data
system or on different systems. Both database files and conventional files can be
partitioned.
Each partition of a file holds a particular range of records and is physically distinct from
any other partition. However, all the partitions belong to the same logical file and
applications view a partitioned file as a single entity.
Because a file can span multiple disks, multiple I/O requests from users can be
serviced concurrently. Different disk drives perform multiple, concurrent reads and
writes of data in a single logical file. Delays caused by transaction queues are reduced,
and total system performance goes up.
By contrast, with conventional disk drives, an entire file must reside on one disk
volume, so concurrent I/O requests to the file are not possible. Each I/O request must
be queued and serviced separately. The result is slower system throughput and longer
response time.
File partitioning is also useful when multiple Integrity NonStop servers are joined in an
Expand network.
Suppose a large library converted its entire card catalog to an online database so that
it could retrieve catalog records more quickly and maintain the catalog more easily. The
library stored this database on a single Integrity NonStop server at the main library, and
the catalog department took responsibility for maintaining the database.
Then, as the library gained additional holdings, it acquired two more buildings
elsewhere in the same city, together with a new Integrity NonStop server for each
building. The library also divided its catalog department into three branches, one in
each of its buildings, and made all three branches jointly responsible for maintaining
the database.
What will happen if the library connects its three Integrity NonStop servers in an
Expand network but leaves the entire database on the headquarters system? Every
time a library cataloger at one of the other buildings uses a workstation to access a
record on the main library system, the cataloger must wait while the request message
travels over a communications line to a server on the main library system and while the
reply from the server travels over the communications line back to the workstation.
The library can reduce network message traffic and network delays by partitioning the
database across all three systems. For example, if the primary key of the database is
the author’s last name or is a composite key that consists of several fields but begins
with the author’s last name, the partitions can be:
•
Records for authors A-G reside on the main library (first branch) system.
•
Records for authors H-P reside on the second branch system.
•
Records for authors Q-Z reside on the third branch system.
Each of the three branches of the catalog department is responsible for maintaining the
range of records in its local partition and needs to go across the network only when it
needs to check records in another partition. The result of the partitioned database is