Mainframe Tutorial
JCL Tutorial
Introduction JCL and JES JCL Statements Fields of JCL Statement JOB statement EXEC Statement and its Parameters JOBLIB and STPELIB DD Statement DD DSN parameter DD DISP(Disposition) Paramter DD DCB Parameter DD UNIT Parameter DD VOLUME Parameter DD SPACE Parameter DD SYSOUT Parameter SYSIN (*) – Input Stream Data DUMMY Parameter SYSUDUMP DD statement SYSABEND DD statement CONCATENATION OF DATASET TEMPORARY DATASET REFERBACK JCL Procedure JCL In-Stream Procedure JCL Cataloged Procedure JCL Symbolic Parameters JCL Overriding Parameters in Proc Utilities, an Overview IEBGENER IEBCOPY IEHPROGM IEBCOMPR IEFBR14 GDG GDG Characteristics GDG Advantages and Coding Rules Creating GDG base Creating,Deleting GDG Dataset(GDS) Altering GDG base Deleting GDG base Concatenating Generations of GDG SORT/MERGE Intro SORT FIELDS MERGE FIELDS INCLUDE Statement OMIT Statement SUM FIELDS OUTFIL Statement OUTREC Statement OUTREC FILEDS or OUTREC BUILD OUTREC OVERLAY OUTREC FINDREP OUTREC IF THEN clauses INREC statement Role of JCL in COBOL Program Lifecycle Example of Running COBOL Program using JCL COBOL Tutorial
COBOL Introduction Overview, History & Importance COBOL Features COBOL Simple Example Program
COBOL Coding Sheet COBOL Program Structure COBOL Character Set COBOL Word Data Names and Identifiers COBOL Literals COBOL Figurative Constants Introduction IDENTIFICATION DIVISION ENVIRONMENT DIVISION CONFIGURATION SECTION INPUT-OUTPUT SECTION DATA DIVISION Data-item (variable) Declaration COBOL LEVEL Number COBOL Data-name and FILLER COBOL PICTURE clause and Data types COBOL EDITING Code characters COBOL VALUE clause Internal Data Represenataion in Mainframe. BCD and Binary Packed Decimal and Zoned Decimal Floating point binary number COBOL USAGE Clause SYNCHRONIZED/SYNC clause and slack bytes JUSTIFIED/JUST clause REDEFINES clause RENAMES clause (Level 66 Item) LEVEL 77 Data Item CONDITION NAME (LEVEL 88 Item) SIGN Clause Nameless data description entry FILE SECTION WORKING-STORAGE SECTION LOCAL-STORAGE SECTION LINKAGE SECTION PROCEDURE DIVISION Structure COBOL Verbs MOVE Verb Group Move using MOVE Quilification of Data Name in MOVE MOVE CORRESPONDING Option MOVE Reference Modification or Substring Move De-Editing using MOVE Aithmatic Verbs - Overview ADD Verb SUBTRACT Verb MULTIPLY Verb DIVIDE Verb ROUNDED Option ON SIZE ERROR Option ADD CORRESPONDING & SUBTRACT CORRESPONDING COMPUTE Verb DISPLAY verb ACCEPT Verb CONDITIONAL Verb : IF Categories of COBOL statements INITIALIZE Verb STOP RUN EXIT PROGRAM GO BACK "EXIT" and "END PROGRAM" Control Statements Intro Selection Statements IF ELSE and Nested IF EVALUATE Statement Iteration Statements Simple PERFORM In-line PERFORM PERFORM THRU/THROUGH PERFORM TIMES PERFORM UNTIL PERFORM VARYING PERFORM WITH TEST BEFORE/AFTER PERFORM for Multi-dimensional arrays Jump Statements CONTINUE Statement NEXT SENTENCE GO TO ALTER Statement String Handling in COBOL INSPECT EXAMINE STRING UNSTRING ARRAY (or TABLE) Single Dimensional ARRAY OCCURS Clause Two Dimensional ARRAY SUBSCRIPT ARRAY INDEX and INDEXING SUBSCRIPT vs INDEX SET Verb Sequential search:"SEARCH" Binary search:"SEARCH ALL" SEARCH vs SEARCH ALL FIles processing Terminologies File Handling Steps Step 1: File Allocation Step 2: File Definition Step 3: OPENing file Step 4: Processing of File READ Statement WRITE Statement REWRITE Statement START Statement DELETE Statement Step 5: CLOSEing file File Error Handling FILE Status Codes COPY Verb for Copybook Sub-programming and Calls Static Call and Dynamic Call Nested Programs END PROGRAM Statement IS GLOBAL clause IS EXTERNAL Clause IS {COMMON / INITIAL} PROGRAM SORT MERGE COBOL Program Lifecycle Compiling & Running COBOL Program COBOL – Database Interface concepts Embedded SQL DB2 Application Programming Host variables DCLGEN SQLCA SQL Queries DB2 Cursors INTRINSIC functions LE and LE callable services COBOL Performance Tuning tips VSAM Tutorial
Introduction VSAM Overview VSAM Cluster Data Componenet, CI, CA Index Componenet VSAM Splits and Spanned records Data set organization techniques KSDS ESDS RRDS LDS Comparison of VSAM types AMS Overview IDCAMS Utility IDCAMS DEFINE CLUSTER Command Defining KSDS Defining ESDS Defining RRDS Defining LDS IDCAMS REPRO Command Loading KSDS Loading ESDS Loading RRDS IDCAMS PRINT Command IDCAMS ALTER Command IDCAMS DELETE Command IDCAMS LISTCAT Command IDCAMS EXPORT Command IDCAMS IMPORT Command IDCAMS MODAL Command Alternate Index Overview Defining Alternate Index Building Index Defining Path VSAM Status codes DB2 Tutorial
DB2 Introduction What is DB2? DB2 Features DB2 Versions and History DB2 vs VSAM DB2 Terminology DB2 and Mainframe DB2 Architecture DB2 Subsystem DB2 Address Spaces DB2 Components DB2 Buffer Pools DB2 Logging DB2 Catalog Database Tablespace Table Index View Alias Synonym Sequence DB2 Object Relationships DB2 Data Types NULL Values What is SQL? DDL DML DCL SELECT INSERT UPDATE DELETE COMMIT and ROLLBACK WHERE Clause Comparison Operators AND OR NOT IN BETWEEN LIKE IS NULL DISTINCT ORDER BY CASE Aggregate Functions Scalar Functions GROUP BY HAVING INNER JOIN OUTER JOIN SELF JOIN Subqueries EXISTS UNION and UNION ALL Creating Tables CREATE TABLE ALTER TABLE DROP TABLE Tablespace Introduction Tablespace Types Partitioned Tablespaces Universal Tablespaces Tablespace States What is an Index? Index Types Unique and Non-Unique Index Clustering Index Composite Index Primary Key Foreign Key UNIQUE CHECK Referential Integrity COBOL and DB2 Embedded SQL EXEC SQL Host Variables SQLCA DB2 Precompiler DBRM DB2 COBOL Compile Process DB2 Program Structure What is a Cursor? DECLARE CURSOR OPEN FETCH CLOSE Cursor with COBOL Cursor with UPDATE Cursor with DELETE Cursor Error Handling SQLCODE SQLSTATE SQLCA SQLCODE +100 SQLCODE -803 SQLCODE -805 SQLCODE -811 SQLCODE -818 SQLCODE -911 SQLCODE -913 DB2 Error Handling in COBOL DBRM Package Collection Plan BIND PACKAGE BIND PLAN REBIND DSN Command IKJEFT01 DB2 Batch JCL DB2 Compile and Bind Process LOAD UNLOAD REORG RUNSTATS COPY RECOVER CHECK DATA CHECK INDEX DB2 Utility JCL Common Production Issues DB2 Job Failures DB2 Locking Lock Types Deadlocks Timeouts Isolation Levels DB2 Recovery DB2 Logs Image Copies EXPLAIN Access Paths Performance Tuning Stored Procedures Triggers CTE MERGE Temporary Tables Partitioning DB2 Security GRANT and REVOKE Real-World DB2 Scenarios DB2 Interview Questions SQL Coding Questions Production Support Scenarios CICS Tutorial
CICS Introduction What is CICS? Why CICS is Used CICS Features CICS vs Batch Processing CICS Terminology CICS Regions CICS Transactions CICS Tasks CICS Versions and History CICS Architecture CICS Region CICS Address Spaces CICS Components CICS Transaction Manager CICS Program Manager CICS Storage Manager CICS File Control CICS Temporary Storage CICS Transient Data CICS Communication What is a Transaction? Transaction ID Transaction Lifecycle Task vs Transaction CICS Command Structure EXEC CICS CICS Command Categories CICS Resource Definitions Common CICS Commands COMMAREA COBOL and CICS CICS-Enabled COBOL Program EXEC CICS Statements CICS Translator CICS Precompile Process CICS Compile and Link DFHEIBLK DFHCOMMAREA CICS Program Structure CICS COBOL Example What is BMS? BMS Maps Physical Map Symbolic Map Mapset DFHMDF DFHMDI DFHMSD Screen Attributes MDT SEND MAP RECEIVE MAP BMS COBOL Program CICS File Control VSAM and CICS READ WRITE REWRITE DELETE STARTBR READNEXT READPREV ENDBR File Definitions File Status Codes Temporary Storage (TS) TS Queues WRITEQ TS READQ TS DELETEQ TS Intra-Partition TS Extra-Partition TS Transient Data (TD) WRITEQ TD READQ TD TD vs TS COMMAREA CHANNEL CONTAINER LINK XCTL RETURN Program Control Static vs Dynamic Calls LINK vs XCTL Passing Data Between Programs Pseudo-Conversational Programming CICS and DB2 Embedded SQL in CICS CICS DB2 Program Structure SQLCA DB2 Connection DB2 Plan DB2 Thread COMMIT in CICS CICS and DB2 COBOL Example CICS DB2 Error Handling Conversational Processing Pseudo-Conversational Processing START RETURN TRANSID RETRIEVE STARTBR Task Control Transaction Flow Synchronization ENQ and DEQ CICS Error Handling RESP RESP2 HANDLE CONDITION HANDLE ABEND HANDLE AID IGNORE CONDITION EIBRESP EIBRESP2 EIBTRNID EIBTASKN Common CICS Errors CEDF Debugging CICS Resources Transaction Definitions Program Definitions File Definitions TD Queue Definitions TS Queue BMS Map Definitions DB2 Definitions CEDA CEDB CEDC Resource Installation CICS Recovery CICS Restart Warm Restart Emergency Restart Dynamic Backout Unit of Work Syncpoint Abend Handling Common Production Issues CICS Job Failures File Problems Transaction Problems Production Troubleshooting CICS Performance CICS Monitoring CICS Statistics CICS Trace Storage Management Threadsafe Programming CICS Security RACF and CICS Multiregion Operation (MRO) Inter-System Communication (ISC) CICS Web Services CICS TCP/IP CICS Modernization CICS COBOL Banking Application CICS and DB2 Application Customer Inquiry Transaction Account Update Transaction CICS Menu-Driven Application End-to-End CICS Project CICS Scenario-Based Questions CICS COBOL Interview Questions BMS Interview Questions CICS DB2 Interview Questions Production Support Questions CICS Coding Questions TSO Tutorial
ISPF Tutorial
MVS Tutorial
Endevor Tutorial
ChangeMan Tutorial
IMS Tutorial
REXX Tutorial
CLIST Tutorial
QMF Tutorial
Common Abends/Errors
Abend Codes Overview S0C7 - Data Exception S0C4 - Protection Exception S0C1 - Operation Exception S322 - CPU Time Exceeded S806 - Load Module Not Found S80A - Out of Storage S222 - Job Cancelled S213 - Open Error SB37 - Out of Space S722 - Sysout Limit Exceeded U4038 - Language Environment Abend ASRA - CICS Program Check AICA - CICS Runaway Task
Mainframe Tips & Tricks
ISPF
ISPF tricks and Tips See unsaved changes with COMPARE SESSION Change a member's USER ID with the G line command Check your region and user details with SAREA Retain commands on the command line with & Find who is holding your dataset (F1 twice) Find PDS members by pattern with 4.12 Browse recently viewed datasets with REFLIST COMPARE command - a SuperCE alternative that pulls lines Autocomplete dataset names with AUTOTYPE Find which PDS holds a member with the MEMBER command Recall your last 25 commands with RETP Open any member fast with the S line command Open any dataset directly with EPDF (skip 3.4) Compare against last save with COMP * X Edit the clipboard and use named clipboards (CUT DISPLAY) Append to the clipboard with CUT APPEND SRCHFOR popup - search up to 6 strings at once Cycle dataset history with one key (NRETRIEV) Recall commands with one key (RETRIEVE) See tape dataset info with the TI command FIND and CHANGE power tips - quotes, PREV, columns, picture strings Sort members by Changed date and FILTER the member list Compare specific columns across files in SuperCE (CMPCOLMN) Wrap text to any width with TF (TF20) Handy commands - SYSNAME, USERID, PANELID, MSGID Send messages to colleagues with TSO SEND
Mainframe Interview Q&A
Troubleshooting
All 500 Articles COBOL (53)
S0C7 data exception during numeric calculation S0C4 protection exception S0C1 operation exception S0C9 divide exception Invalid numeric data in a PIC field Packed-decimal sign nibble problem COMP-3 field length mismatch Data truncation after MOVE Incorrect results after REDEFINES OCCURS table subscript out of range Reference modification length error Uninitialized working-storage field Input record layout mismatch Output file contains shifted fields Incorrect decimal arithmetic Rounding differences in financial calculations Numeric-edited field conversion problem PIC clause causes unexpected storage length Binary field overflow COMP and COMP-5 value mismatch Incorrect sign handling Date field contains invalid values Program loops without reaching termination PERFORM THRU range skips paragraph Nested PERFORM changes control flow CALL parameter mismatch LINKAGE SECTION parameter layout mismatch COPYBOOK version mismatch Duplicate paragraph or data name Condition-name 88 level not behaving as expected INITIALIZE clears more data than expected STRING statement pointer overflow UNSTRING delimiter handling error INSPECT count or replace gives wrong result READ statement fails to detect end of file OPEN EXTEND behaves unexpectedly CLOSE reports an I/O error File organization differs from program definition Compiler option changes runtime behavior LE condition handler masks the original issue Program works in test but fails in production Unexpected low-values or spaces in a field Incorrect record count after processing Batch program produces duplicate output Job ends with S0C7 Job ends with S0C4 S0C1 operation exception in production S0C4 protection exception diagnosis S0C7 data exception diagnosis S0C8 fixed-point overflow S0C9 fixed-point divide exception S0CA decimal overflow S0CB decimal divide exception VSAM (56)
File status 35 on OPEN INPUT File status 10 unexpected end of file File status 23 record not found File status 39 file attribute mismatch File status 92 logic error File status 30 permanent I/O error VSAM file status 23 record not found VSAM file status 35 dataset missing VSAM file status 39 attribute conflict VSAM file status 10 end of file VSAM file status 22 duplicate key VSAM file status 21 sequence error VSAM file status 92 logic error VSAM file status 90 environment error VSAM OPEN fails despite catalog entry IDCAMS DEFINE CLUSTER fails IDCAMS REPRO returns error IDCAMS LISTCAT output is confusing KSDS key length mismatch KSDS alternate index path unavailable ESDS relative record assumptions fail RRDS record number is invalid VSAM dataset reaches CI or CA split pressure VSAM dataset performance degrades after growth VSAM file locked by another job VSAM cluster cannot be deleted PATH entry points to wrong AIX AIX and base cluster become inconsistent REPRO copies fewer records than expected REPRO rejects records with duplicate keys File status is not checked after OPEN COBOL FD layout differs from VSAM attributes Record length varies unexpectedly VSAM dataset defined with wrong SHAREOPTIONS Catalog alias resolves unexpected dataset Dataset is uncataloged but still allocated Alternate index upgrade fails IDCAMS VERIFY reports index issue Backup restore leaves file unavailable File is empty after successful batch run Record key is not in expected position START command returns unexpected status READ NEXT returns records in unexpected order WRITE fails on an existing key REWRITE fails after READ DELETE fails for a found record VSAM access path causes slow random reads Dataset volume migration affects access File status 97 after OPEN RLS access behaves differently from non-RLS VSAM cluster is defined with incorrect FREESPACE Data component and index component sizing issue Input file has EBCDIC character mismatch Record layout changed without coordinated deployment Batch and online jobs contend for the same VSAM file VSAM status code lacks enough detail for diagnosis JCL (52)
JCL syntax error before job execution JCL ERROR due to missing comma or parameter JOB card parameter rejected EXEC statement references missing program DD statement references a missing dataset DISP parameter causes dataset allocation failure Dataset already exists during allocation Temporary dataset unavailable to later step GDG generation not found GDG base limit or roll-off issue PROC symbolic parameter not substituted Procedure override does not take effect COND parameter skips an unexpected step IF/THEN/ELSE logic selects wrong branch Return code causes downstream step to be skipped MAXCC is unexpectedly high Job ends with S322 time limit exceeded Job ends with SB37 space abend Job ends with SD37 space abend Job ends with SE37 extent limit reached System reports dataset in use DISP=MOD appends when replacement was expected DISP=OLD causes enqueue wait Cataloged dataset cannot be located Unit or volume parameter causes allocation error DUMMY DD changes program behavior SYSIN control cards are not read as expected In-stream data delimiter is missing SORT step produces zero records DFSORT INCLUDE condition filters all records DFSORT OUTREC positions are incorrect SORT field format does not match input data Duplicate records remain after sort ICETOOL count differs from expected RESTART skips required setup step Checkpoint restart duplicates records Job runs longer after input volume increases Job abends only with month-end data Job output is missing from expected spool class JES holds a job unexpectedly Initiator shortage delays batch start Scheduler dependency prevents job submission Return code differs between environments Input dataset DCB attributes mismatch RECFM or LRECL mismatch Job uses stale load module Load library concatenation resolves wrong module Restart after partial output risks duplicate posting S322 time limit exceeded SB37 insufficient space condition SD37 secondary allocation unavailable SE37 extent limit reached Db2 (50)
SQLCODE -911 deadlock or timeout SQLCODE -913 resource unavailable SQLCODE -805 package not found SQLCODE -818 consistency token mismatch SQLCODE -904 unavailable resource SQLCODE -911 versus -913 diagnosis SQLCODE +100 no row found SQLCODE -305 null indicator missing SQLCODE -302 input value too large SQLCODE -803 duplicate key SQLCODE -530 foreign key violation SQLCODE -531 parent delete restricted SQLCODE -532 parent row delete restriction SQLCODE -407 null inserted into non-null column SQLCODE -180 invalid date or time SQLCODE -181 invalid date or time value SQLCODE -220 column definition mismatch SQLCODE -204 object not defined SQLCODE -206 column not found SQLCODE -440 routine not found SQLCODE -551 authorization failure SQLCODE -922 connection authorization failure SQLCODE -913 during batch update Cursor returns duplicate rows Cursor skips expected rows Cursor remains open across commit COMMIT frequency causes lock contention ROLLBACK leaves application state inconsistent Host variable length mismatch NULL handling fails in embedded SQL Indicator variable has wrong value Static SQL package bind failure REBIND changes access path performance RUNSTATS produces unexpected plan changes Query regresses after data growth Table space in restrictive state REORG job fails or is delayed LOAD utility rejects input rows UNLOAD output count does not match table count Index is not used by a query Query performs table space scan unexpectedly Deadlocks increase during peak processing Lock escalation slows batch jobs Db2 connection fails after deployment Plan or package points to wrong collection SQL statement works in SPUFI but not program Decimal conversion error in SQL host variable Timestamp comparison returns unexpected rows Commit scope causes partial business updates Long-running unit of work holds locks CICS (51)
ASRA transaction abend AEI0 program not found AEY9 resource unavailable AICA runaway task condition MAPFAIL after RECEIVE MAP MAPONLY or DATAONLY map display issue COMMAREA length mismatch Channel/container data missing LINK program receives incorrect data XCTL does not return to caller RETURN TRANSID loop starts unexpectedly RESP and RESP2 indicate command failure File control NOTOPEN condition NOTFND response for existing record DUPREC response on WRITE LENGERR on file or program command INVREQ response from CICS command PGMIDERR after deployment Transaction definition points to wrong program Program is not enabled Newcopy does not load expected module CICS program runs old version Transaction times out under load Task waits on a resource Temporary storage queue item missing Transient data queue write fails TS queue grows unexpectedly TD queue trigger does not fire Terminal receives blank map fields BMS symbolic map layout mismatch PF key handling behaves incorrectly EIBTRNID or EIBTRMID unexpected Abend occurs only for one transaction ID Transaction dump is unavailable CSMT log shows repeated abends CICS region appears hung CICS response time suddenly increases Storage violation reported Temporary storage shortage File is disabled after error MQ call returns unexpected reason code CICS Db2 thread acquisition fails Syncpoint backs out updates unexpectedly Unit of work remains open too long Security check rejects transaction Resource definition differs across regions Program works in test region but fails in production Transaction abends after copybook change Pseudo-conversation loses state Task limit reached during peak traffic MQ call causes ASRA after reason code ignored z/OS (38)
S0C2 privileged operation exception S0C5 addressing exception S0C6 specification exception Uxxxx user abend diagnosis System completion code has a reason code Job log does not show the first failure Multiple abends occur in one job SYSOUT is missing or incomplete SDSF cannot locate expected job Job is in held status unexpectedly Initiator shortage delays batch processing Dataset enqueue causes job wait Catalog search returns unexpected result IEC message indicates allocation failure IGD message indicates SMS allocation issue SMS class selection differs across environments Volume is full or unavailable System logger messages appear during outage Address space uses unexpected CPU High CPU after application deployment Paging activity increases sharply Storage shortage affects batch processing WLM service class impacts response time Started task fails during initialization Started task remains in restart loop Console message repeats continuously IPL-related dependency causes service failure SMF records are missing from expected interval SYSLOG timestamps confuse incident timeline Dump is not produced after abend IPCS dump analysis starts with incomplete evidence LOGREC points to recurring hardware or software event Program fails only on one LPAR Cross-system resource contention slows processing Job succeeds on one system but fails on another Load library search order selects wrong module Authorization error prevents dataset access Backup or recovery step reports success but data is stale Security (50)
RACF dataset access denied User cannot log on to TSO User ID is revoked or suspended Password or passphrase change fails Group connection is missing Dataset profile does not match resource name Generic profile grants unexpected access Access works in test but fails in production Started task cannot access required dataset Surrogate job submission is rejected OPERATIONS attribute is misunderstood SPECIAL authority is not effective as expected RACF command returns insufficient authority Program access to protected resource fails CICS transaction security check fails Db2 authorization failure after deployment USS permission denied for file Z/OS UNIX user mapping issue SSH login to USS fails Certificate expired or not trusted TLS handshake fails after certificate renewal Key ring lacks required certificate Digital certificate label mismatch AT-TLS policy does not match connection Password phrase policy blocks sign-on Group owner mismatch prevents profile administration RACF audit records are missing Unexpected access appears in SMF audit data Resource profile is defined in wrong class Class is inactive or not RACLISTed RACLIST refresh does not show expected change User has conflicting group permissions Access check differs between batch and TSO Dataset profile permits read but blocks update CICS region user lacks resource authority MQ queue access is denied FTP transfer fails due to security policy Certificate chain is incomplete Service account lacks least-privilege access Expired credential breaks scheduled job Emergency access change is not reflected Security change causes application outage USS umask produces incorrect file permissions File owner differs after deployment RACF profile cleanup risks removing required access Auditor requests evidence of access review User cannot submit a job under another ID Authorization failure is misdiagnosed as missing dataset Certificate works on one LPAR but not another Security configuration drift across environments IMS (20)
IMS transaction returns unexpected status IMS program receives no input message IMS database PCB status indicates failure IMS call returns GE status IMS call returns GB status IMS database segment not found IMS database update is backed out IMS PSB or PCB definition mismatch IMS program works in test but fails in production IMS region cannot access database IMS message queue backlog grows IMS transaction response time increases IMS dependent region fails to initialize IMS batch job cannot open database IMS restart recovery takes longer than expected IMS log dataset space problem IMS checkpoint restart reprocesses work IMS authorization failure IMS transaction abend lacks clear root cause IMS database reorganization affects availability MQ (29)
MQ reason code 2035 not authorized MQ reason code 2059 queue manager unavailable MQ reason code 2085 unknown object name MQ reason code 2087 remote object unavailable MQ reason code 2009 connection broken MQ queue depth reaches limit MQ message remains on queue MQ backout queue fills up MQ poison message repeatedly reprocessed MQ trigger monitor does not start application MQ channel enters retry state MQ channel authentication fails MQ TLS certificate error MQ message gets truncated by application buffer MQ message format mismatch MQMD fields are not populated as expected MQPUT fails during peak traffic MQGET waits longer than expected Syncpoint rollback returns message to queue Persistent message recovery behaves unexpectedly Dead-letter queue receives unexpected messages Remote queue definition points to wrong target Clustered queue routing differs from expectation MQ listener fails after restart Queue manager startup reports log issue MQ connection from CICS fails Application does not handle MQ completion code Message expiry removes expected work Duplicate message processing after restart Networking (50)
TCP/IP connection to mainframe is refused Connection times out from distributed application DNS name resolves to wrong address Port is not listening on z/OS Firewall blocks application connection TLS handshake fails between application and z/OS Certificate hostname does not match Certificate trust chain is incomplete Expired certificate breaks API call Z/OS Connect API returns HTTP 401 Z/OS Connect API returns HTTP 403 Z/OS Connect API returns HTTP 404 Z/OS Connect API returns HTTP 500 REST request payload fails validation JSON field mapping loses data API response schema changes unexpectedly API call latency increases after deployment Distributed caller disconnects mid-transaction Character encoding corrupts returned text EBCDIC-to-UTF-8 conversion changes characters Fixed-width record sent as delimited data Network transfer truncates large response FTP transfer uses wrong mode SFTP authentication fails File transfer completes with wrong record count API gateway timeout while backend continues Connection pool exhaustion affects mainframe calls Load balancer routes to unhealthy endpoint Service endpoint differs between environments HTTP retry causes duplicate business transaction Idempotency key is not honored OAuth token expires during long operation SOAP service returns fault after schema update MQ bridge delays message delivery DNS cache retains old endpoint IPv4 and IPv6 behavior differs Network route changes cause intermittent failures Firewall rule change breaks batch transfer Remote client sends unexpected code page Mainframe API returns valid HTTP status but business error Large payload exceeds configured limit Request header missing required value API works from one network segment only Distributed trace cannot correlate mainframe request Connection reset occurs under load API authentication succeeds but authorization fails Maintenance restart leaves stale connections Retry policy amplifies an outage Service account credential rotation breaks integration Batch file transfer arrives after dependent job starts DevOps (49)
Zowe CLI login fails Zowe CLI profile points to wrong endpoint Zowe Explorer cannot connect to z/OS Certificate validation blocks Zowe connection Z/OSMF REST API returns unauthorized Z/OSMF endpoint is unavailable Zowe command returns a confusing HTTP error USS command fails due to permissions Git checkout changes source record formatting COBOL source encoding breaks build Copybook dependency missing in CI pipeline Build uses wrong compiler options Pipeline deploys stale load module Promotion package contains wrong program version Link-edit resolves wrong module Binder reports unresolved external reference Compile succeeds but link-edit fails Test environment differs from production runtime Automated test data is not repeatable CI job fails due to unavailable agent Deployment leaves source and load module out of sync Rollback restores code but not configuration Configuration drift breaks application Secret or credential rotation breaks pipeline Static analysis flags legacy COBOL patterns Automated test misses packed-decimal edge case API contract changes break consumer Java-to-COBOL call has parameter mismatch Python USS script fails under batch environment Shell script uses incorrect environment variable Scheduler environment differs from interactive shell Containerized service cannot reach mainframe endpoint Cloud integration retries create duplicate transactions Observability logs omit correlation ID Deployment succeeds but transaction uses old program Blue-green cutover sends traffic to wrong region Migration changes sort order or collating sequence Data conversion loses leading zeros Test compares EBCDIC and ASCII incorrectly API modernization exposes different error behavior Performance regresses after runtime upgrade Dependency version mismatch breaks build Release approval blocks emergency fix Pipeline has no post-deployment verification Automated restart repeats a failed workload Monitoring alert lacks actionable context Change record misses dependency mapping Parallel rollout causes incompatible copybook versions Legacy batch job has undocumented upstream dependency Batch (2)
Mainframe Quiz
Mainframe Online Tests
Mainframe Jokes/Memes
Mainframe Tools
Contact us
About usDo you know if you want to see information for any Tape, simply passing “I” does not work for tape dataset. But if your mainframe is CA configured, you can issue “TI” command against that tape to see information
Below is how description will be displayed:-
Backward
