The Tachyon Operating System creates and maintains a number of control blocks. In most cases the control blocks are at least partially filled in with reasonable information. In some cases an empty control block is allocated to allow programs to reference it without causing an addressing exception.
The SWA control blocks are always allocated below the 16 megabyte line.
This allows older programs to access the SWA control blocks such as the
JFCB, JFCX and SIOT.
| Control Block | Notes |
|---|---|
| ACEE Accessor Environment Element |
The job step ACEE is created. |
| APF Table Authorized Program Facility Table |
The static form of the APF table is built, based on the PROGxx.ini configuration files. |
| AMB Access Method Block |
One AMB is created for each open VSAM data or index component. |
| AMBL Access Method Block List |
One AMBL is created for each open VSAM ACB. |
| AMCBS Access Method Control Block Structure |
If the VSAM feature is licensed, the AMCBS is created and partially initialized, otherwise an empty AMBCS is built. |
| AMDSB Access Method Data Statistics Block |
One AMDSB is created for each open VSAM data or index component. |
| ARDB Address Range Definition Block |
One ARDB is created for each open VSAM data or index component. |
| ASCB Address Space Control Block |
One ASCB and its extensions (the ASSB and ASXB) are built for the active address space. The address space is for ASID 1. |
| ASTE Address Space Second Table Entry |
One ASTE is built for the active address space. |
| ASVT Address Space Vector Table |
The ASVT has only the entry for the ASCB of the active address space. |
| BUFC Buffer Control Block |
Buffers are allocated for each open VSAM ACB unless MACRF=UBF is specified. The BUFC control blocks are not compatible with those built by z/OS. |
| BUFCB Buffer Pool Control Block |
A buffer pool is allocated for QSAM data sets as they are opened. |
| CDE Contents Directory Entry |
A CDE and the associated Extent List (XTLST) is built for each non-LPA module loaded via the LINK(X), LOAD or XCTL(X) services. |
| CIB Command Input Buffer |
A CIB is allocated for each MODIFY or STOP operator command entered. |
| CICB Compatibility Interface Control Block |
A CICB is allocated for each BSAM and QSAM DCB opened for a subsystem data set. |
| CSD Common System Data |
The CSD is created. |
| CSCB Command Scheduling Control Block |
One CSCB is built for the active job. The CSCB extension (CSCX) is also created. |
| CVT Communications Vector Table |
The CVT and its extensions (CVTVSTGX, CVTXTNT1, CVTXTNT2, SCVT and ECVT) are created. The CVT and ECVT are initialized based on the IEASYSxx.ini BCP parameter. |
| DCB Data Control Block |
The Link List and JOBLIB/STEPLIB DCBs are created. |
| DCQ Device Class Queue |
The DCQ is created and the DASD queue is initialized. |
| DDIB Data Definition Information Block |
A DDIB is created for all data sets in the active job step with an associated DD PATH. |
| DEB Data Extent Block |
The DEB and the DEB extension are created for each open DCB. |
| DFA Data Facilities Area |
The DFA is initialized based on the IEASYSxx.ini DFP parameter. An empty Data Facilities Vector Table (DFVT) is also allocated. |
| DSAB Data Set Attributes Block |
A DSAB is created for each DD statement in the active job step. |
| DUCT Dispatchable Unit Control Table |
An empty DUCT is allocated. |
| DVCT Device Characteristics Table |
The DVCT is created and fully initialized. |
| EPIE Extended Program Interruption Element |
An EPIE is allocated by the SPIE/ESPIE service. |
| IOB Input / Output Block |
When a BSAM or BPAM DCB is opened, a partial IOB is built for each of the number of channel programs (NCP) requested. |
| JCT Job Control Table |
The JCT, its extension (the JCTX), its Account Control Table (ACT) and the Job Management Record (JMR) are created for the active job. |
| JESCT Job Entry Subsystem Communication Table |
The JESCT and the JESCT Pagable Extension (JESPEXT) are created. However, no subsystems are supported. |
| JFCB Job File Control Block |
A JFCB is created for every DD statement in the active step. The Job File Control Block Extension (JFCE) may also be created. |
| JSAB Job Scheduler Address Space Control Block |
One JSAB is built for the active job. |
| JSCB Job Step Control Block |
One JSCB is built for the active job step. |
| LCCA and LCCAVT Logical Configuration Communication Area |
One empty LCCA is chained off of the LCCAVT. |
| LDA Local Data Area |
The LDA is built for the active job step and contains the region size information. |
| LLE Load List Entry |
One LLE is built for each module loaded via the LOAD service. |
| LLT Link List Table |
The LLT, its extension (the LLTX) and the Dynamic LNKLST Control Block (DLCB) are built, based on the LNKLSTxx.ini configuration files. |
| LPAT Link Pack Area Table |
The LPAT is built, based on the LPALSTxx.ini configuration files. |
| LPDE Link Pack Directory Entry |
One LPDE is built for each module found in the data sets specified in the LPALSTxx.ini configuration files, forming the Pagable Link Pack Directory. |
| MPL MVS Assist Parameter List |
The SVC Table pointer in the MPL is initialized. |
| NUCMAP Nucleus Map |
The nucleus map is created and initialized with the Tachyon Operating System nucleus module and SVC routines. |
| OAPB, OASB, OTCB, PPSD, PRLI and THLI USS Control Blocks |
These control blocks are allocated and initialized once the process is “dubbed” by invoking one of the UNIX System Services. |
| OCVT and OEXT USS Common Vector Table and USS Common External Control Block |
If the IEASYSxx.ini OMVS parameter is set, the OCVT and OEXT areas are initialized. |
| PCCA and PCCAVT Physical Configuration Communication Area |
One PCCA is chained off of the PCCAVT. The CPU identification information is initialized from the LOADxx.ini CPUID parameter value or its default. |
| PIE Program Interruption Element |
A PIE is allocated by the SPIE/ESPIE service. |
| PLH Place Holder |
Place Holders are built for each open VSAM ACB. The PLH control blocks are not compatible with those built by z/OS. |
| PRB Program Request Block |
A PRB and the associated Extended Status Block (XSB) are built each time the LINK(X) or SYNCH(X) service is called. |
| RAX RSM Address Space Block Extension |
The RAX is built for the active job step and contains the MEMLIMIT value. |
| SAFV System Authorization Facility Router Vector Table |
An empty SAFV is allocated. |
| SCA SPIE/ESPIE Control Area |
The SCA is initialized for the active task. |
| SCB STAE Control Block |
One SCB is created for each active STAE, ESTAE or ESTAEX. |
| SCCB Service Call Control Block |
The SCCB is created. |
| SCT Step Control Table |
The SCT, its extension (the SCTX) and its Account Control Table (ACT) are created for the active job step. |
| SFT System Function Table |
The SFT is initialized with the PC numbers for the supported system routines. |
| SHID System Host Identifier |
The SHID is initialized with the information from the LOADxx.ini CPUID parameter value or its default. |
| SIOT Step Input / Output Table |
An SIOT is created for every DD statement in the active job step. |
| SVC Table | The SVC Table is initialized with the entries for the supported SVCs and the routines in the IEASVCxx.ini configuration files. The ESR tables for SVCs 109, 116, 122 and 137 are also built. |
| SVRB Supervisor Request Block |
One SVRB and the associated Extended Status Block (XSB) are built each time a type 2, 3 or 4 SVC routine is called. |
| SVT Supervisor Vector Table |
An empty SVT is allocated. |
| SYMBT Symbol Table |
The static system symbol table is initialized with the entries from the IEASYMxx.ini configuration files. |
| TCAST Terminal Control Address Space Table |
An empty TCAST is allocated. |
| TCB Task Control Block |
One TCB and the associated Secondary Task Control Block (STCB) is built for the active task. |
| TIOT Task Input / Output Table |
The TIOT for the active job step is built from the DD statements. |
| UCB Unit Control Block |
A single UCB is created for a 3390 device with an address of X'0100' and volume serial of SYSRES. All DASD data sets are allocated to this unit. |
| VAT Valid AMBL Table |
One or more VAT entries are built as VSAM ACBs are opened. |