In Oracle Integration Cloud (OIC), you can use the REPLACE function to replace occurrences of a specified substring within a string with another substring. This function is often used within expressions and mapping activities to manipulate and transform data. Here’s the syntax for the REPLACE function in OIC:

REPLACE(source_string, old_substring, new_substring) 

• source_string: The original string in which you want to perform the replacement.
• old_substring: The substring you want to replace within the source_string.
• new_substring: The substring that will replace occurrences of old_substring in the source_string.

Here are some examples of how to use the REPLACE function in Oracle Integration Cloud:

1. Replace all occurrences of a substring within a string: REPLACE(‘Hello, world! Hello, Oracle!’, ‘Hello’, ‘Hi’) — Output: ‘Hi, world! Hi, Oracle!’ 
2. Replace a specific substring within a string:                 REPLACE(‘123-456-7890’, ‘-‘, ”) — Output: ‘1234567890’ 
3. Replace multiple occurrences of a substring within a string: REPLACE(‘Red, green, blue, red’, ‘red’, ‘yellow’) — Output: ‘Red, green, blue, yellow’ 
4. Replace a substring with an empty string to remove it: REPLACE(‘Remove this substring.’, ‘Remove this ‘, ”) — Output: ‘substring.’