Loads data into the tables of the database.
You can use the RMU Load command to:
o Perform the initial load of an Oracle Rdb database.
o Reload a table after performing a restructuring operation.
o Load an archival database.
o Move data from one database to another.
o Load security audit records from an OpenVMS security audit
table into the database being audited, or into a different
database than the one being audited.
o Load additional rows into an existing table. (However, note
that it cannot be used to modify existing rows.)
o Import data into a database from an application that generates
RMS files.
You can load data using either of the following two methods:
o A single-process method
This was the only method available prior to Oracle Rdb V7.0.
The single process method uses one process to both read the
input file and load the target table.
o A multiprocess method, also called a parallel load
The parallel load method, which you specify with the Parallel
qualifier, enables Oracle RMU to use your process to read
the input file and use one or more executors (subprocesses
or detached slave process, depending on additional factors)
to load the data into the target table. This results in
concurrent read and write operations, and in many cases,
substantially improves the performance of the load operation.
By default, Oracle RMU sets up a parallel load operation as
follows:
o Your process serves as the load operation execution manager.
o Each storage area (partition) in the table being loaded is
assigned an executor.
o Each executor is assigned four communications buffers.
(You can override this default with the Buffer_Count option to
the Parallel qualifier.)
o Each communications buffer holds the number of rows defined by
the Row_Count qualifier.
Once the executors and communications buffers are set up, the
parallel load operation processes the input file as follows:
1. Your process begins reading the input file and determines the
target storage area for each row in the input file.
2. Your process places each row in the communications buffer for
the executor assigned to the data's target storage area.
3. When an executor's first communications buffer becomes full,
it begins loading the data into the target storage area.
4. If your process has another portion of data ready for a given
executor before that executor has completed loading its first
buffer of data, your process places the next portion of data
in the second communications buffer for that executor.
5. Each executor, concurrent with each of the other executors,
loads the data from its buffers.
6. Your process continues reading, sorting, and assigning data to
each executor (by placing it in that executor's communication
buffer) until all the data from the input file has been
sorted, assigned, and loaded.
The Row_Count qualifier and Parallel qualifier (which provides
the Executor_Count and Buffer_Count options) give you the ability
to fine tune the Parallel load operation.
See the Oracle Rdb Guide to Database Design and Definition for
tips on optimizing the performance of the load operation.
Additional Information:
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