The data contained in a codefile is read-only when created by a compiler, and is protected from general modification; however, there are some normal (and safe) circumstances that can update the contents of a codefile.
For example:
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When the WFL MODIFY command is used to apply a file, task, library, or database attribute equation.
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When the MP (Mark Program) system command is used to modify codefile privileges.
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When the MCP updates the SEG0 information, such as the execution count or estimated stack size, when the program is executed or terminated.
In these situations, the MCP recreates any present codefile verification data, regardless of the CODEVERIFYCHECK setting, to ensure that the verification data remains valid.
