Two types of abend codes, user abends and system abends (S0C Abends). User abends format is Unnnn, where nnnn is a decimal user abend code. System abends follow the format of Snnn, where nnn is a hexadecimal abend code. S0C Abends are the abnormal ending of Job & when it happens a message from the JCL or Fault Analyzer will indicate that you have a condition code (or return code) such as – S0C1, S0C4, S0C7, etc. We will go through four major S0C abends in this article. When a system abend occurs, the operating system can generate a system dump. System dumps are written to ddname SYSMDUMP, SYSABEND, or SYSUDUMP. There are S0C1-9 & S0CB abends & in this post, we will discuss common abends like S0C1, S0C4, S0C5 & S0C7

S0C Abends: S0C1 (Operation Exception)

Abend Text: The system detected an operation exception (System Completion Code=0C1)

Description: An attempt was made to execute an invalid machine instruction operation code. The operation code is either invalid or is for an instruction that is not available on this CPU. This failure is usually due to a branch to an invalid storage location, as might occur in a load module with unresolved external references, or when a branch to an address outside of a program occurs.

Possible Causes:

• Subscript error.
• AMODE is set as 24, but a branch was attempted to a 31-bit or (on z/OS) a 64-bit address.
• Tried to read a file that was not open.
• Misspelled DDNAME followed by attempted I/O to same file.
• Error in parameters passed to subroutines. Calling a program and the program was not included during link edit. 
• Missing DD card followed by attempted I/O to same file.
• Recording mode was wrong, or density was incorrect.
• Bad load module, possible bad object deck. Executing a program with an unresolved external reference. 
• Calling a program and the program was not included during link edit. 
• Mixing compile options RES and NORES in different modules.
• An uncontrolled loop moved data on top of instructions. 
• COBOL – Subroutine prog ID was the same as the entry name tried to call within COBOL sort I/O procedure.
• COBOL – Tried to call a subroutine which could not be found.
• COBOL – Incomplete DCB for SORTIN file.
• COBOL – Using sort verb, DDNAME was not SORTOUT when the”giving” option was used.
• COBOL – Executing sort-using after opening SORTIN file.

User Action: Correct the program logic or construction error and rerun the job.

Scenario: A program attempts to divide a number by zero, triggering S0C1.

Resolution:

• Implement Zero Checks: Before performing division, add code to verify that the divisor is not zero.
• Handle Zero Cases Gracefully: If zero division is possible, implement alternative logic or error handling to prevent the abend.

Scenario: A calculation results in a value too large or too small for the designated data field, causing S0C1.

Resolution:

• Utilize Larger Data Types: Accommodate potential overflow or underflow by using data types with wider ranges (e.g., COMP-3 instead of COMP-2).
• Implement Error Handling: Detect overflow/underflow conditions and handle them gracefully, preventing abends.

Scenario: A program tries to convert incompatible data types, such as moving a numeric value to a character field of insufficient size, leading to S0C1.

Resolution:

• Ensure Data Type Compatibility: Verify that data types align with intended operations.
• Use Explicit Conversion Functions: Employ built-in functions like MOVE FUNCTION NUMVAL for controlled numeric-to-character conversions.
• Check Target Field Size: Ensure character fields are large enough to accommodate converted values.

S0C Abends: S0C4 (Protection Exception)

Description: Protection exception. An invalid machine address was calculated by the program. This ABEND is caused by a hardware detected virtual address translation error, or a storage protection violation.

Possible Causes:

• COBOL – Invalid address was referenced due to subscript error or bad parameter passed.
• COBOL – In group move, receiving record variable length defined incorrectly.
• COBOL – Tried moving variable length record that was larger than target field size.
• COBOL – Tried to read or write a file which was not open.
• COBOL – Used DD DUMMY with logic that moves high values to FD.
• COBOL – Tried to call within COBOL SORT I/O procedure.
• COBOL – Tried to “GOBACK” in the SORT output procedure.
• COBOL – Linkage Area Ordering is not in sync with calling and called program.
• COBOL – Missing Select statement (during compile).
• The blocksize and record size were specified as equal for variable length records. Tried moving variable length record that was larger than target field size.
• An uncontrolled loop moved data on top of instructions. 
• Referencing a field in a record of a closed file e.g. attempting to read a file after end of file reached.
• Referencing an item in Linkage-Section when there was no PARM= in the JCL. 
• Calling/called programs have different length for items passed in Linkage Section with COBOL Sort, doing a STOP RUN or GOBACK while an input or output procedure is still running.

User Action: Correct the program logic error that generated the invalid address or storage reference. When analyzing the dump, remember that the PSW saved when an 0C4 abend occurs may point at the failing instruction or it may point at the next instruction after the failing instruction. Check to ensure that your program is obtaining, using, and freeing storage properly.Moving data to a zero address or to an address less than 512 (decimal) is a very frequent cause of this abend.

Scenario: A loop iterates through an array, but a calculation error causes the subscript to exceed its maximum value, triggering the S0C4.

Resolution:

• Correct the Calculation: Meticulously examine the loop’s logic and adjust the calculation to ensure the subscript stays within bounds.
• Implement a Guard Condition: Add a check within the loop to terminate it before the subscript oversteps its boundaries, preventing the abend.

Scenario: A program attempts to access a character within a string using a subscript greater than the string’s length, resulting in the S0C4.

Resolution:

• Utilize String Functions: Employ built-in functions like LENGTH to determine the string’s length and ensure subscripts stay within valid limits.
• Implement String Validation: Add checks before accessing string elements to prevent out-of-bounds attempts, proactively warding off the abend.

Scenario: An array is declared with a specific size, but data is inadvertently loaded beyond its capacity, leading to the S0C4 when accessing elements beyond the allocated space.

Resolution:

• Verify Data Integrity: Thoroughly inspect data loading procedures to guarantee that data fits within the array’s boundaries.
• Consider Dynamic Arrays: If data size is unpredictable, explore dynamic arrays that can expand as needed, providing flexibility and avoiding abends.

S0C Abends: S0C5 (Addressing Exception)

Description:An address developed and used by the ABENDing program lies outside of the available virtual storage on the processor.

Possible Causes:

• Indexing, Subcripting outside the program’s assigned limits.
• Un-initialized index
• Attempt to read an unopened input file
• A missing or misspelled DD statement.
• An attempt to close a dataset second time
• An input/output instruction is terminated because an open is unable to complete
• Falling through into an ENTRY statement 
• Transferring control into the middle of a SORT procedure.

User Action: Correct the program logic the refers to invalid address/storage.

Scenario: A program attempts to access an array element beyond its declared size, triggering S0C5.

Resolution:

• Implement Array Bounds Checks: Validate subscripts before accessing array elements.
• Utilize Dynamic Arrays: Consider dynamic arrays that expand as needed to accommodate fluctuating data sizes.
• Implement Error Handling: Gracefully handle array overflow situations to prevent abends.

Scenario: A program attempts to access an array element beyond its declared size, triggering S0C5.

Resolution:

• Implement Array Bounds Checks: Validate subscripts before accessing array elements.
• Utilize Dynamic Arrays: Consider dynamic arrays that expand as needed to accommodate fluctuating data sizes.
• Implement Error Handling: Gracefully handle array overflow situations to prevent abends.

Scenario: An invalid pointer, pointing to an unauthorized memory location, is used, causing S0C5.

Resolution:

• Meticulously Initialize Pointers: Ensure pointers are set correctly before use.
• Scrutinize Pointer Calculations: Verify the accuracy of pointer arithmetic.
• Utilize Debugging Tools: Employ debuggers to examine pointer values and track down invalid references.

Scenario: A program tries to modify a read-only memory area, resulting in S0C5.

Resolution:

• Review Data Definitions: Ensure data areas intended for modification are declared as writable.
• Check External Constraints: Be mindful of system-imposed read-only restrictions.

S0C Abends: S0C7 (Data Exception)

Description:  Data was incorrect format for the instruction that attempting to process it. The ABEND can occur when packed decimal instruction are used.

Possible Causes:

• Un-initialized index or subscript. Coding past the maximum allowed sub script
• Fields in decimal arithmetic overlap incorrectly
• Index /Subscript value incorrect and invalid data was referenced
• The decimal multiplicand has too many high-order significant digits
• Data fields was not initialized, blanks were read into a field designed to be processed with packed decimal instruction.
• Program attempting to do math on illegal data. 
• Data is not numeric, but should be. Numeric operation on non-numeric data
• Moving ZEROS to group item whose subordinate items are packed-decimal
• Uninitialized packed-decimal fields. 
• Record description is wrong. Field starts or ends in the wrong place in the record. 

User Action: Correct the format of the data/initialize the data item that is being computed.

Scenario: A program attempts to divide a number by zero, triggering S0C7.

Resolution:

• Implement Zero Checks: Before performing division, add code to verify that the divisor is not zero.
• Handle Zero Cases Gracefully: If zero division is a valid scenario, implement alternative logic or error handling to prevent the abend.

Scenario: A program tries to convert incompatible data types, such as moving a numeric value to a character field, leading to S0C7.

Resolution:

• Ensure Data Type Compatibility: Verify that data types align with intended operations.
• Use Explicit Conversion Functions: Employ built-in functions like MOVE FUNCTION NUMVAL for controlled numeric-to-character conversions.

Scenario: A program accesses a data field before it’s been assigned a value, causing S0C7.

Resolution:

• Initialize Data Fields: Assign initial values to all data fields before using them.
• Utilize Debugging Tools: Debuggers can pinpoint uninitialized fields and help track their origin.

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