When you run a CDC session, the PowerCenter Data Transformation Manager (DTM) allocates buffer memory to the session based on the

DTM Buffer Size

value on the

Properties

tab of the session properties. The DTM divides the memory into buffer blocks based on the

Default Buffer Block Size

setting on the

Config Object

tab of the session properties.

If you suspect that buffer memory is insufficient, enable the collection of performance details in the CDC session. Then review the difference between the performance counters

4.1 Time in PowerExchange Processing

and

4.4 Elapsed Time

. If the elapsed time is much larger that the PowerExchange processing time, buffer memory constraints might exist. To improve performance of the CDC session, try adjusting the

DTM Buffer Size

and

Default Buffer Block Size

properties.

For optimal CDC performance, set these session properties to create a large number of small blocks. Informatica recommends the following settings:

Do

not

set these session properties to

auto

. The

auto

option creates a small number of large blocks, which can degrade CDC session performance. The

auto

option is intended for bulk data load processing.