Dataloader/MP Reference Manual

DataLoader/MP Reference Manual—424148-003
7-1
7 Recovery Strategies
This section discusses strategies for planning DataLoader/MP run scenarios so that
you will be able to rerun DataLoader/MP and successfully load your database if you
experience a failure during the load operation.
Why Is Recovery Important?
The contents of a database are crucial. To ensure that data is valid, it must be loaded
accurately, whatever its source. Loading a database can be a one-time activity or part
of a daily, weekly, or monthly job schedule.
As with any process, there is always the possibility of failure. Failure — that of
software, hardware or power — can occur at any time while batch loading is taking
place. You must plan for recovery from these failures in a way that maintains the
validity of the databases.
Creating a plan that will work reliably and efficiently is a challenge. Many databases
are too large to be backed up before running a batch load job. Therefore, you must
build recovery possibilities into your load strategy.
Defining Load
The term load is used for all kinds of DataLoader/MP applications. To load a database
is to populate it in one of three ways:
•
Start with an empty table and write rows of data.
•
Append rows to a table that already contains data.
•
Start with a table that contains data, then amend its data by updating some rows,
appending some rows, and even deleting rows.
In this discussion, loading refers to loading new information into the database in the
third way. Some of the new information takes the form of new rows, some takes the
form of updated rows, and some takes the form of deleted rows.
DataLoader/MP can be used to load a NonStop SQL database in many ways. It can be
as simple as a single DataLoader/MP process putting data directly into a single table. It
can be as complex as dozens, or hundreds, of DataLoader/MP processes arranged in
multiple stages, with these processes taking input from multiple sources, processing it,
and using it to load many different tables, some directly and some through LOAD or
APPEND. Clearly, it is impossible to describe a specific recovery plan for each possible
scenario. Following are a number of different general approaches you can use to
develop an overall recovery plan for your loading scenario.