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Mainframe data, made visible.

● RECORD DECODER · customers.dat · FB 71 · CP037ROW 3 OF 3

CUST-ID ..... 100236

CUST-NAME ... LEE CHEN

CUST-BAL .... X'4040404040' ◂ S0C7 RISK

ORDER-COUNT . 0

F1=HelpF7=UpF8=DownF10=CSVF11=JSONon this device

Byte maps, colour-linked hex, annotated JCL and plain-English error codes. Everything runs on your device — free, no sign-in, nothing uploaded.

ENTER ▸ Decode a file Look up a code

11tools for data, JCL and sort

178abend, SQL, CICS, MQ and security codes

7EBCDIC code pages

0 bytesever sent to a server

Tools

OPTION ===> type a number in the command boxAll tools

01Copybook viewer

Paste a COBOL copybook and see every field's position, length and type.

Use this when you need a field's position, length or the total record length (LRECL) from a copybook.

02Record decoder

Read a mainframe data file with its copybook as a table, CSV or JSON.

Use this when you have a mainframe file (FB or VB) and its copybook and want to read it as a table, CSV or JSON.

03Packed decimal calculator

Turn numbers into packed, zoned or binary hex, and back.

Use this when you need the hex bytes of a COMP-3, zoned or binary field, or want to know what some hex means.

04EBCDIC converter

Convert text to EBCDIC hex and back, in seven code pages.

Use this when you need to turn text into EBCDIC hex, or EBCDIC hex back into text, for a given code page.

05Mainframe date converter

Julian YYDDD, CYYDDD, Lilian days and STCK clock values to real dates.

Use this when a file or dump shows a date as YYDDD, CYYDDD, 0CYYDDDF, a Lilian day or a STCK clock value.

06Block size and space calculator

Best BLKSIZE for your record length and the space a file needs on 3390.

Use this when you are choosing BLKSIZE for a new file or working out how many tracks or cylinders it needs.

07JCL checker

Find common JCL mistakes and read each statement in plain English.

Use this when a job fails with a JCL error, or you want to check JCL before you submit it.

08JCL generator

Fill in a form to get ready-to-run JCL for everyday jobs.

Use this when you need a ready-to-edit job for an everyday task such as allocating, copying, deleting or sorting a data set.

09DFSORT helper

Build SORT, INCLUDE and OUTREC statements, or explain existing ones.

Use this when you need SORT, INCLUDE/OMIT or OUTREC statements, or want to understand ones you already have.

10COBOL debugger

Step through a COBOL program line by line and watch every field change.

Use this when you want to see why a COBOL program or Db2 stored procedure gives a wrong result or an S0C7, one statement at a time.

11Why was I denied?

Paste a RACF ICH408I message to see why access was refused and what to ask for.

Use this when a job or logon failed with ICH408I (often with abend 913) and you want to know why and what to ask for.

12Site search

Search by code or in plain words; results come only from this site's pages.

Use this when you have a code or a description of a problem and do not know which page or tool to open.

NEW · FOR AI ASSISTANTSYour AI assistant, now fluent in mainframe.Give Claude, Cursor or Copilot MainframeKit's JCL, DFSORT, code and copybook checks. Runs on your PC.Set it up ▸

Error codes, explained

All 178 codes

S0C1 · S0C2 · S0C4

Abend codes36 codes

-805 · -811 · -803

Db2 SQLCODEs40 codes

ASRA · AEXL · ASRB

CICS codes44 codes

2009 · 2016 · 2018

MQ reason codes41 codes

ICH408I · S047 · S306

Security codes17 codes

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One problem, two doors

Learn it on Mainframe Path. Do it with MainframeKit.

S0C7 · DATA EXCEPTION

LEARN ITWhy bad packed data abendsMainframe Path DO ITFind the bad field in the fileMainframeKit

JCL ERROR

LEARN ITHow JCL errors happenMainframe Path DO ITCheck your JCL before you submitMainframeKit

READING A COPYBOOK

LEARN ITCOBOL data types explainedMainframe Path DO ITSee every field's offset and lengthMainframeKit