In z/OS control blocks are used to manage the work and resources of the system. They are represented internally as areas containing specific information pertaining to events, activity and status occurring within the infrastructure’s operation. Control blocks are usually chain to one another and can span many areas of an operating system’s internal structure. Knowledge of control blocks are useful in finding out information about the system.
To access a control block you need you need to know:
Below you find a table with z/OS control blocks and their associated addresses. A good starting point is the Communications Vector Table (CVT). Its address is always held at offset 16 (Hex 10) in the Prefix System Area (PSA) and the PSA can always be found at virtual address zero.
| Control block | Block address | Block description |
|---|---|---|
| <LINK 152>ACEE</link> | ASXB+X'C8' | Accessor Environment Element |
| ACEX | ACEE+X'98' | ACEE Extension (current) |
| APHT | CSVT+X'0C'+X'08' | APF List |
| <LINK 153>ASCB</link> | <LINK 148>PSA</link>+X'224' | Address Space Control Block |
| ASCBJBNI | <LINK 153>ASCB</link>+X'AC' | ASCB (Current) Batch Jobname (or zero) |
| ASCBJBNS | <LINK 153>ASCB</link>+X'B0' | ASCB (Current) Start/Mount/Logon |
| ASMVT | <LINK 154>CVT</LINK>+X'2C0' | Auxiliary Storage Mgt Vector Table |
| ASSB | <LINK 153>ASCB</link>+X'150' | Ad Space Secondary Block (current) |
| ASVT | <LINK 154>CVT</LINK>+X'22C' | Address Space Vector Table |
| ASXB | <LINK 153>ASCB</link>+X'6C' | Address Space Extension Block |
| BASEA | <LINK 154>CVT</LINK>+X'94' | Master Scheduler Resident Data Area |
| BASEX | BASEA+X'C8' | Basea Extension |
| CAUB | VAB+X'08' | Common Area User Block (current) |
| CAUBS | GDA+X'194' | System CAUB |
| CAUBU | GDA+X'19C' | Unowned CAUB |
| CCT | RMCT+X'04' | SRM CPU management Control Table |
| CPPL | LWA+X'254' | TSO CPPL |
| CDA | IOVT+X'18' | Configuration Data Area |
| CPMT | CMCT+X'0C' | Channel Path Measurement Table |
| CSCB | <LINK 153>ASCB</link>+X'38' | Command Scheduling Control Block |
| CSCX | CSCB+X'DC' | CSCB Extension |
| CSD | <LINK 154>CVT</LINK>+X'294' | Common System Data |
| CSVT | ECVT+X'E4' | Contents Supervisor Table |
| <LINK 154>CVT</LINK> | X'10' | Communication Vector Table |
| CVTEXT | <LINK 154>CVT</LINK>+X'148' | Communications Vector Table Extention |
| CVTFIX | <LINK 154>CVT</LINK>-X'100' | Communications Vector Table Prefix |
| DACA | JESCT+X'78' | Device allocation Communication Area |
| DFA | <LINK 154>CVT</LINK>+X'4C0' | Dfp Id Table |
| DFVT | <LINK 154>CVT</LINK>+X'4C0'+X'2C' | |
| DLCBC | ECVT+X'88' | Dynamic Linklist Ctl Blk (current) |
| DLCBU | ASSB+X'EC' | Dynamic Linklist Ctl Blk (user) |
| DMCT | RMCT+X'B4' | Domain Table |
| DPTB | RCVT+X'2E8' | Racf Dynamic Parse Table |
| DQE | SPQAx | Vsm Descriptor Queue Element (One Of Zillions) |
| DSDT | RCVT+X'E0' | RACF Data Set Descriptor Table |
| ECVT | <LINK 154>CVT</LINK>+X'8C' | Extended CVT |
| EDT | DACA+X'60' | Eligible device table |
| EDT1 | EDTL+X'10' | First EDT |
| EDT2 | EDTL+X'14' | Second EDT |
| EDTL | DACA+X'60' | EDT list |
| GDA | <LINK 154>CVT</LINK>+X'230' | Global Data Area |
| GVT | <LINK 154>CVT</LINK>+X'1B0' | GRS Vector table |
| HID | <LINK 154>CVT</LINK>+X'42C' | CPU Information Iosdshid |
| HSMASCB | <LINK 154>CVT</LINK>+X'3DC'+X'08' | HSM ASCB |
| ICT | RMCT+X'08' | I/O Management Control Table |
| IOCOM | <LINK 154>CVT</LINK>+X'7C' | I/O Communication area |
| IOVT | IOCOM+X'D0' | IOS Vector Table |
| IPA | ECVT+X'188' | Initialization Parameter Area |
| <LINK 150>JCT</LINK> | <LINK 151>JSCB</LINK>+X'104' | Job Control Table |
| JESCT | <LINK 154>CVT</LINK>+X'128' | JES Communication Table |
| <LINK 151>JSCB</LINK> | <LINK 149>TCB</LINK>+X'B5' | Job/Step Control Block |
| JSCBACT | <LINK 151>JSCB</LINK>+X'15C' | Active Job/Step Control Block |
| JSTCB | <LINK 149>TCB</LINK>+X'7C' | Job Step Tcb |
| LCCA | <LINK 148>PSA</link>+X'210' | Logical Configuration Com Area |
| LCCAVT | <LINK 154>CVT</LINK>+X'300' | Lcca Vector Table |
| LDA | <LINK 153>ASCB</link>+X'30' | Local Data Area |
| LLE | <LINK 149>TCB</LINK>+X'24' | Last Load List Element |
| LLT | <LINK 154>CVT</LINK>+X'4DC' | Link List Table |
| LLTC | DLCBC+X'10' | Link List Table (current) |
| LLTU | DLCBU+X'10' | Link List Table (user) |
| LLTX | CSVT+X'04' | Link List Table Volumesxxx |
| LNKLST | <LINK 154>CVT</LINK>+X'4DC' | Link List Table |
| LPAQ | <LINK 154>CVT</LINK>+X'BC' | Lpa Cde List |
| LPAR | STGS+X'48'+X'2EC' | Lpar information |
| LPAT | VSTGX+X'38' | Link Pack Area Table |
| LSCT | RMCT+X'3C' | Logical Swap Control Table |
| LUV | EDT+X'10'+X'1C' | |
| LWA | ASXB+X'14' | TSO LWA |
| MCT | RMCT+X'0C' | Storage Management Control Table |
| NUCMAP | <LINK 154>CVT</LINK>+X'4B0' | Nucleus Map |
| OUCB | <LINK 153>ASCB</link>+X'90' | Resources Manager User Cont Blk |
| OUSB | ASXB+X'80' | Resources Manager User Swappable Blk |
| OUXB | <LINK 153>ASCB</link>+X'94' | Resources Manager User Extension Blk |
| PCCA | <LINK 148>PSA</link>+X'208' | Physical Configuration Comm Area |
| PCCAVT | <LINK 154>CVT</LINK>+X'2FC' | PCCA Vector Table |
| PIT | HCCT+X'4F0' | Initiator List (Changes Frequently With Jes) |
| <LINK 148>PSA</link> | 0. | Prefixed Save Area |
| PSCB | <LINK 151>JSCB</LINK>+X'108' | TSO Protected Step Control Block |
| PVT | <LINK 154>CVT</LINK>+X'164' | RSM Page Vector Table |
| RAB | <LINK 153>ASCB</link>+X'178' | RSM Address Space Block |
| RAX | <LINK 153>ASCB</link>+X'16C' | RSM Add Space Block Extension |
| RB | <LINK 149>TCB</LINK> | Request blocks for this task |
| RCE | <LINK 154>CVT</LINK>+X'490' | RSM Control and Enumeration Area |
| RCT | RMCT+X'E4' | SRM Resource Control Table |
| RCVI | RCVT+X'184' | RACF Identity cache communication vector |
| RCVT | <LINK 154>CVT</LINK>+X'3E0' | RACF Communication Vector Table |
| RCVX | RCVT+X'258' | RACF Communication Vector Table Extension |
| RIT | PVT+X'04' | RSM Internal Table |
| RMCA | RMCT+X'14' | System Resource Manager Control Area |
| RMCT | <LINK 154>CVT</LINK>+X'25C' | System Resources Manager Ctrl Table |
| RMEX | RMCT+X'28' | SRM External Entry Poiny Descriptor Table |
| RMPT | RMCT+X'10' | SRM |
| RTCT | <LINK 154>CVT</LINK>+X'23C' | Recovery/Termination Control Table |
| RSH | PVT+X'14' | RSM RECOVERY REFRESH TABLE |
| SCCB | <LINK 154>CVT</LINK>+X'340' | Service Call Control Block |
| SCTE | WMCT+X'24' | wlm srm |
| SCT | <LINK 151>JSCB</LINK>+X'148' | Step Control Table |
| SCTX | SCT+X'44' | Step Control Table Extension |
| SCVT | <LINK 154>CVT</LINK>+X'C8' | Secondary Communication Vector Table |
| SHDR | <LINK 154>CVT</LINK>+X'250' | SLIP Header |
| SFT | <LINK 154>CVT</LINK>+X'304' | |
| SJB | PIT+X'04' | |
| SMCA | <LINK 154>CVT</LINK>+X'C4' | System Management Facilities Control Table |
| SMCX | SMCA+X'178' | SMCA Extension |
| SPQA | SPQE+X'08' | VSM Subpool Queue Anchors |
| SPQE | <LINK 149>TCB</LINK>+X'18' | VSM Subpool Queue Element |
| SPT | GDA+X'88' | VSM Subpool Table |
| SSCT | JESCT+X'18' | Subsystem Communications Vector Table |
| SSCVT | JESCT+X'18' | Subsystem Communications Vector Table |
| SSIB | JSCBACT+X'13C' | Subsystem Identification Block |
| SSVT | SSCT+X'10' | Subsystem Vector Table |
| STCB | <LINK 149>TCB</LINK>+X'138' | Secondary Task Control Block (TCB) |
| STGS | <LINK 154>CVT</LINK>+X'31C' | Measurement Facility Control Block |
| SVCT | SCVT+X'84' | Svc table |
| SVCTAB2 | SCVT+X'88' | Svc Update Recording Table |
| SVCTABLE | SCVT+X'84' | Svc Table |
| SVRB | <LINK 153>ASCB</link>+X'10' | |
| SVT | <LINK 154>CVT</LINK>+X'364' | Supervisor Vector Table |
| <LINK 149>TCB</LINK> | <LINK 148>PSA</link>+X'21C' | Task Control Block |
| TCBFSA | <LINK 149>TCB</LINK>+X'70' | TCB First Save Area |
| TCT | <LINK 149>TCB</LINK>+X'A4' | System Management Facilities Timing Control Table |
| TCTSTOR | TCT+X'08' | TCT Storage Area |
| TIOT | <LINK 149>TCB</LINK>+X'0C' | Task Input/Output Table (current) |
| TOT | <LINK 148>PSA</link>+X'7FC' | System trace operand table (TOT) |
| TSB | <LINK 153>ASCB</link>+X'3C' | Terminal Status Block (current) |
| TSVT | <LINK 154>CVT</LINK>+X'9C' | TSO/E Vector Table |
| UCM | <LINK 154>CVT</LINK>+X'64' | Unit Control Module |
| ULUT | IOVT+X'08' | Ucb Lookup Table |
| UPT | PSCB+X'34' | |
| VAB | ASSB+X'F0' | VSM Address space Block |
| VATLST | DACA+X'0C' | Volume Attributs List |
| VSTGX | <LINK 154>CVT</LINK>+X'4AC' | Virtual Storage Extension of CVT |
| VTAMCVT | CVTEXT+X'40' | |
| WMCT | RMCT+X'20' | WMCT wlm srm |
| WMST | RMCT+X'18' | WMST wlm srm |
| XMD | SVT+X'94' | Cross_Memory Directory (in PCAUTH) |
| XMSE | ASSB+X'48' | Cross_Memory Control Block (current) |