Rule Definition
Expensive operations compared to substring and concatenation operator for CHAR data types and NUM datatypes. Some concatenation operations like CHAR and PACK/DECIMAL will require string processing vs CHAR processing (see item above for cost). Comments are generated into the COBOL program indicating which statements cause String processing to occur (in a performance considerations section in the initial comments).

Remediation
Try to reduce the use of copyStr and compareStr

EGL Best Practices: Coding For Performance. November 10, 2009. Edition 2