Every item here traces back to a real, documented failure mode covered elsewhere on this site, not a generic checklist template.
File organization: SEQUENTIAL vs. LINE SEQUENTIAL
A flat text file that opens fine on z/OS can throw file status 35 on AIX or Linux COBOL if the SELECT clause still says SEQUENTIAL.
VSAM cluster is not empty before first OPEN
An empty (but correctly cataloged) VSAM file returns file status 35 on some platforms, which looks identical to a missing file.
COMP-3 (packed decimal) fields are genuinely numeric before arithmetic
The single most common production abend, S0C7, comes from arithmetic on an uninitialized or corrupted packed field.
DD/dataset allocation happens before the step runs, not during it
Covers the majority of file-status-35 and abend-S806 cases: the program is fine, the JCL or environment isn't ready yet.
Record layout (copybook) matches the file's actual current version
A file status 04 (record length mismatch) usually means the program is reading a file written under a different copybook version.
Embedded SQL: package/plan was rebound after any program recompile
SQLCODE -818 is specifically a bind-timestamp mismatch between the running load module and the bound package.