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5. Compare the computed values.

Table 9 1 provides computations for selected database types. The argument for

the DB2

SUM()

 function is converted to

DECIMAL

 type, because in most cases the

SUM()

 function returns the same data type as its argument, which can cause

arithmetic overflow. For example, when calculating the sum on an

INTEGER

column, if the result exceeds the

INTEGER

 data type range, error

SQL0802N

is

generated:

Arithmetic overflow or other arithmetic exception occurred

Converting the argument to

DECIMAL

 eliminates the error.

Table 9 1   Aggregations for data migration verification

Data type

MySQL operation

DB2 operation

numeric(

sum(val)

sum(cast(val as

sion>,)

decimal(31,)))

date

sum(trunc( val   to_date(

sum(cast(days(val) as

 0001/01/02 , yyyy/mm/dd )))

decimal(31,1)))

variable length

sum(length(val))

sum(cast(length(val) as

character

decimal(31,0)))

fixed length

sum(length(rtrim(val)))

sum(cast(length(rtrim(val))

character

as decimal(31,0)))

9.3  Code and application testing

The most important part of the testing process is to verify that each component of

the system functions as it was before migrating. All components of the RDBMS

system should be verified whether they are working properly.

9.3.1  Application code check

The scope of application testing depends on the migrated application.

For self built applications the testing process should be started with the

application queries. All queries should be independently tested to ensure that

they return the expected results. With the application queries successfully

migrated, the surrounding client programs should be rebuilt, and then the

application should be tested against the target database. Each module of the

application and possibly each screen form should be run and be checked for

errors or improper functionality. All supported interfaces should also be checked.

The very important issue is to document all the tests conditions such as what

operations were performed, which application screens were opened, what input

data was used for testing, and what the result was. For larger projects, the

 Chapter 9. Testing and tuning

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