Availability Guide for Application Design

Designing Applications for Change
Availability Guide for Application Design—525637-004
10-28
Physically Reconfiguring the Database
•
Changing the objects that a SQL program accesses; for example, accessing a
different table with the same program
•
Upgrading the SQL program to a new revision level
•
Making changes to the objects that the application accesses; for example, logical
changes such as adding a column to a table or physical changes such as moving a
table or adding an index
Traditionally, operations such as these require you to bring the application down while
you recompile all SQL statements.
NonStop SQL/MP includes the ability to dynamically resolve names at execution time
and some options in the SQL compiler that increase availability. These features allow
you to selectively eliminate or, at least, reduce any downtime caused by these kinds of
changes. Compiling your programs with the appropriate SQL compiler options will
make online upgrade possible at a later time.
Depending on the application changes, similarity checks might work with high-
availability compilation to achieve a reduction in downtime by eliminating unnecessary
recompilation. By endowing your program with the ability to perform similarity checks,
you can eliminate or minimize the need for recompilation when the application needs to
change.
Reorganizing a NonStop SQL/MP table that has become inefficient through the
addition and deletion of rows and columns can be achieved without special design
considerations by executing the FUP RELOAD command. As indicated in Section 4,
Data Protection and Recovery, such reorganization can be achieved without taking the
database offline for any Enscribe file or NonStop SQL/MP table organized as a B-tree.
Re-creating or adding to a NonStop SQL/MP table, perhaps because of data migration
from systems of a vendor other than HP, can be quite time-consuming. However, with
the DataLoader/MP product, applications can be built quickly to provide parallel loading
for each partition in the table. This greatly reduces the unavailability of the database.
For additional overview information about the NonStop SQL/MP product, refer to the
Introduction to NonStop SQL/MP. For additional information about DataLoader/MP,
refer to the DataLoader/MP Reference Manual.
Physically Reconfiguring the Database
The HP NonStop SQL/MP product allows you to add an index, move a partition, split a
partition, or move the boundaries of a partition without incurring extensive database
outages.
Adding an index orders data according the value specified in key columns. As a result,
queries that use these key columns run quickly. Moving a partition moves a partition
from one disk to another disk. Splitting a partition makes two partitions out of one.