Sequence Generator

1. What is a sequence generator transformation?

A Sequence generator transformation generates numeric values. Sequence generator transformation is a passive transformation.

2. What is the use of a sequence generator transformation?

A sequence generator is used to create unique primary key values, replace missing primary key values or cycle through a sequential range

of numbers.

3. What are the ports in sequence generator transformation?

A sequence generator contains two output ports. They are CURRVAL And NEXTVAL.

4. What is the maximum number of sequence that a sequence

Generator can generate?

The maximum value is 9,223,372,036,854,775,807

5. When you connect both the NEXTVAL and CURRVAL ports to a target, what will be the output values of these ports?

NEXTVAL CURRVAL

1 2

2 3

3 4

4 5

5 6

6. What will be the output value, if you connect only CURRVAL to the target without connecting NEXTVAL?

The integration service passes a constant value for each row.

7. What will be the value of CURRVAL in a sequence generator transformation?

CURRVAL is the sum of "NEXTVAL" and "Increment By" Value.

8. What is the number of cached values set to default for a sequence generator transformation?

For non-reusable sequence generators, the number of cached values is set to zero.

For reusable sequence generators, the number of cached values is set to 1000.

9. How do you configure a sequence generator transformation?

The following properties need to be configured for a sequence Generator transformation:

Start Value

Increment By

End Value

Current Value

Cycle

Number of Cached Values

10.Suppose we have 100 records coming from the source. Now for a target column population we used a Sequence generator. Suppose the Current Value is 0 and End Value of Sequence generator is set to 80. What will happen? 

Ans. End Value is the maximum value the Sequence Generator will generate. After it reaches the End value the session fails with the following error message:

TT_11009 Sequence Generator Transformation: Overflow error.

Failing of session can be handled if the Sequence Generator is configured to Cycle through the sequence, i.e. whenever the Integration Service reaches the configured end value for the sequence; it wraps around and starts the cycle again, beginning with the configured Start Value.

Q35. What are the changes we observe when we promote a non reusable Sequence Generator to a reusable one? And what happens if we set the Number of Cached Values to 0 for a reusable transformation?

Ans. When we convert a non reusable sequence generator to reusable one we observe that the Number of Cached Values is set to 1000 by default; and the Reset property is disabled.

When we try to set the Number of Cached Values property of a Reusable Sequence Generator to 0 in the Transformation Developer we encounter the following error message:

The number of cached values must be greater than zero for reusable sequence transformation.

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