Document revision date: 19 July 1999

When creating a new process, if the set of real balance slots is allocated, then a virtual balance slot is created and the owner of a real balance slot is selected and transitioned to the virtual balance slot. The new process is created in the real balance slot. Processes are transitioned (faulted) back to a real balance slot as they are scheduled to execute on a CPU.

Bit	Result
0	Enables VBS. All other VBS enables are subordinate to this enable. The default is disabled.
1	Enables the creation of a map for process-based direct I/O, allowing the process with direct I/O (DIO) outstanding to be transitioned to a virtual balance slot. Without DIO maps, a process with DIO outstanding retains its real balance slot for the duration of the DIO. This reduces the pool of available real balance slots for timesharing, which may result in a higher rate of faulting into the limited set of real balance slots. The default is enabled.
2-7	Reserved to Compaq for future use.

VBSS_ENABLE2

This cell is used for enabling and disabling VBS dynamic capabilities that are valid only when VBS is enabled. The following table indicates the result for each value:

Bit	Result
0	Enables VBS to perform first-level data reduction when switching processes. The default is enabled.
1	Enables VBS to perform second-level data reduction when switching processes. The default is enabled.
2	Requests VBS to perform an optimization that detects empty private page table pages on the modified list and frees them directly to the free list versus writing them to the page file. The default setting is enabled.
3-7	Reserved to Compaq for future use.

VCC_FLAGS (A)

VCC_FLAGS enables or disables virtual I/O caching. The virtual I/O cache is a file-oriented disk cache that reduces I/O bottlenecks and improves performance. Cache operation is transparent to application software and requires very little system management. This functionality provides a write-through cache that maintains the integrity of disk writes while significantly improving read performance. The virtual I/O cache works on standalone systems and in an OpenVMS Cluster environment if all nodes in the cluster support virtual I/O caching.

By default, virtual I/O caching is enabled. The values of the VCC_FLAGS parameter are as follows:

• VCC_FLAGS = 1 enables caching
• VCC_FLAGS = 0 disables caching

By default, memory is allocated for caching 6400 disk blocks. This requires 3.2 MB of memory. Use the system parameter VCC_MAXSIZE to control memory allocation in units of disk blocks.

VCC_MAX_CACHE

VCC_MAX_LOCKS

VCC_MAXSIZE (A)

The virtual I/O cache cannot shrink or grow. Its size is fixed at system startup.

This special parameter is used by Compaq and is subject to change. Do not change this parameter unless Compaq recommends that you do so.

VCC_MINSIZE

This special parameter is used by Compaq and is subject to change. Do not change this parameter unless Compaq recommends that you do so.

VCC_PTES

The virtual I/O cache automatically shrinks and grows, depending on your I/O workload and how much spare memory your system has. As your I/O workload increases, the cache automatically grows, but never to more than the maximum size. When your applications need memory, the cache automatically shrinks.

This special parameter is used by Compaq and is subject to change. Do not change this parameter unless Compaq recommends that you do so.

VCC_WRITE_DELAY

VCC_WRITEBEHIND

VECTOR_MARGIN (D)

The default value of the VECTOR_MARGIN parameter is 200_10 .

VECTOR_PROC

This parameter is not used on Alpha systems.

VIRTUALPAGECNT (A,G,M)

If you use SYS$UPDATE:LIBDECOMP.COM to decompress libraries and the VIRTUALPAGECNT setting is low, make sure you set the PGFLQUOTA field in the user authorization file to at least twice the size of the library.

At installation time, AUTOGEN automatically sets an appropriate value for VIRTUALPAGECNT. The value depends on the particular configuration---the type and number of graphics adapters on the system, if any exist. You cannot set VIRTUALPAGECNT below the minimum value required for your graphics configuration.

Because the VIRTUALPAGECNT setting supports hardware address space rather than system memory, do not use the value of VIRTUALPAGECNT that AUTOGEN sets to gauge the size of your page file.

Starting with OpenVMS Alpha V7.0, VIRTUALPAGECNT is an obsolete parameter. Note, however, that the parameter remains in existence on Alpha systems for compatibility purposes and has a default and maximum value of %X7FFFFFFF. SYSBOOT and AUTOGEN enforce this default value.

VMS*

VOTES (A)

WINDOW_SYSTEM (D)

WLKSYSDSK

WPRE_SIZE (D)

This special parameter is used by Compaq and is subject to change. Do not change this parameter unless Compaq recommends that you do so.

WPTTE_SIZE (D)

This special parameter is used by Compaq and is subject to change. Do not change this parameter unless Compaq recommends that you do so.

WRITABLESYS

This special parameter is used by Compaq and is subject to change. Do not change this parameter unless Compaq recommends that you do so.

WRITESYSPARAMS (D)

On Alpha systems, WRITESYSPARAMS indicates that parameters are modified during SYSBOOT and are written out to ALPHAVMSSYS.PAR by STARTUP.COM.

This special parameter is used by Compaq and is subject to change. Do not change this parameter unless Compaq recommends that you do so.

WSDEC (A,D,M)

On VAX systems, WSDEC specifies the number of pages by which the limit of a working set is automatically decreased at each adjustment interval (which is quantum end). At a setting of 35, for example, the system decreases the limit of a working set by 35 pages each time a decrease is required.

On Alpha systems, WSDEC specifies the number of pagelets by which the limit of a working set is automatically decreased at each adjustment interval (which is quantum end). At a setting of 35, for example, the system decreases the limit of a working set by 35 pagelets each time a decrease is required.

WSINC (A on Alpha,D,M)

On VAX systems, WSINC specifies the number of pages by which the limit of a working set is automatically increased at each adjustment interval (which is quantum end). At a setting of 150, for example, the system increases the limit of a working set by 150 pages each time an increase is required. On VAX systems, the default value is 150 512-byte pages.

On Alpha systems, WSINC specifies the number of pagelets by which the limit of a working set is automatically increased at each adjustment interval (which is quantum end). At a setting of 150, for example, the system increases the limit of a working set by 150 pagelets each time an increase is required. On Alpha systems, the default value is 2400 512-byte pagelets (150 8192-byte Alpha pages).

A value of 0 for WSINC disables the automatic adjustment of working set limits for all processes. Limits stay at their base values. You can disable the automatic adjustment of working set limits on a per-process basis by using the DCL command SET WORKING_SET.

WSMAX (A,G,M)

This is intended to assist managers of systems that host large numbers of users whose working sets are not large. Systems whose user bases consist of a small number of users (or processes) that require large amounts of physical memory (for example, simulations) might need to set MIN_WSMAX to a value that satisfies the requirements of those processes.

WS_OPA0

XFMAXRATE (D)

XQPCTL2

This special parameter is used by Compaq and is subject to change. Do not change this parameter unless Compaq recommends that you do so.

XQPCTLD1

This special parameter is used by Compaq and is subject to change. Do not change this parameter unless Compaq recommends that you do so.

ZERO_LIST_HI (A,D)

Compaq-supplied devices are attached to the UNIBUS or Q-bus adapters according to the following basic rules:

• A device of type A is always at a fixed and predefined control and status register (CSR) address; the device always interrupts at a fixed and predefined vector address; only one example of device A can be configured in each system.
• A device of type B is identical to type A except that 1 through n examples can be configured in a single system. Examples 2 through n are also located at fixed and predefined CSRs and vector addresses.
• Devices of type C (1 through n of them) are always at fixed and predefined CSR addresses; however, the interrupt vector addresses vary according to what other devices are present on the system.
• Devices of type D (1 through n of them) are at CSR addresses and vector addresses that vary according to what other devices are present on the system.

CSR and vector addresses that vary are called floating addresses. The devices must be located in floating CSR and vector space according to the order in which the devices appear in the SYSGEN device table (see Table K-1). The SYSGEN device table lists all the type A and type B devices supported by the operating system. It also lists the type C and type D devices that are recognized by SYSGEN's autoconfiguration procedure.

The base of floating vector space is 300₈. The base of floating CSR space is 760010₈.

K.1 SYSGEN Device Table (VAX Only)

Table K-1 lists the characteristics of all Compaq devices. This table indicates the following information for each device type:

• Device name
• Device controller name
• Interrupt vector
• Number of interrupt vectors per controller
• Vector alignment factor
• Address of the first device register for each controller recognized by SYSGEN (the first register is usually, but not always, the CSR)
• Number of registers per controller
• Device driver name
• Indication of whether the driver is supported

Devices not listed in Table K-1 are the following ones:

• Devices not supplied by Compaq with fixed CSR and vector addresses. These devices have no effect on autoconfiguration. Customer-built devices should be assigned CSR and vector addresses beyond the floating address space reserved for Compaq-supplied devices.
• Compaq-supplied floating-vector devices that the AUTOCONFIGURE command does not recognize. Use the CONNECT command to attach these devices to the system.

Table K-1 SYSGEN Device Table (VAX Only)

Device Name	Controller Name	Vector	Number of Vectors	Vector Alignment	CSR/Rank	Register Alignment	Driver Name	Support
CR	CR11	230	1	---	777160	---	CRDRIVER	Yes
DM	RK611	210	1	---	777440	---	DMDRIVER	Yes
LP	LP11	200 170 174 270 274	---	---	777514 764004 764014 764024 764034	---	LPDRIVER	Yes
DL	RL11	160	1	---	774400	---	DLDRIVER	Yes
MS	TS11	224	1	---	772520	---	TSDRIVER	Yes
DY	RX211	264	1	---	777170	---	DYDRIVER	Yes
DQ	RB730	250	1	---	775606	---	DQDRIVER	Yes
PU	UDA	154	1	---	772150	---	PUDRIVER	Yes
PT	TU81	260	1	---	774500	---	PUDRIVER	Yes
XE	UNA	120	1	---	774510	---	XEDRIVER	Yes
XQ	QNA	120	1	---	774440	---	XQDRIVER	Yes
OM	DC11	Float	2	8	774000 774010 774020 774030 . . . 32 units maximum	---	OMDRIVER	No
DD	TU58	Float	2	8	776500 776510 776520 776530 . . . 16 units maximum	---	DDRIVER	Yes
OB	DN11	Float	1	4	775200 775210 775220 775230 . . . 16 units maximum	---	OBDRIVER	No
YM	DM11B	Float	1	4	770500 770510 770520 770530 . . . 16 units maximum	---	YMDRIVER	No
OA	DR11C	Float	2	8	767600 767570 767560 767550 . . . 16 units maximum	---	OADRIVER	No
PR	PR611	Float	1	8	772600 772604 772610 772614 . . . 8 units maximum	---	PRDRIVER	No
PP	PP611	Float	1	8	772700 772704 772710 772714 . . . 8 units maximum	---	PPDRIVER	No
OC	DT11	Float	2	8	777420 777422 777424 777426 . . . 8 units maximum	---	OCDRIVER	No
OD	DX11	Float	2	8	776200 776240	---	ODDRIVER	No
YL	DL11C	Float	2	8	775610 775620 775630 775640 . . . 31 units maximum	---	YLDRIVER	No
YJ	DJ11	Float	2	8	Float	8	YJDRIVER	No
YH	DH11	Float	2	8	Float	16	YHDRIVER	No
OE	GT40	Float	4	8	772000 772010	---	OEDRIVER	No
LS	LPS11	Float	6	8	770400	---	LSDRIVER	No
OR	DQ11	Float	2	8	Float	8	ORDRIVER	No
OF	KW11W	Float	2	8	772400	---	OFDRIVER	No
XU	DU11	Float	2	8	Float	8	XUDRIVER	No
XV	DV11	Float	3	8	775000 775040 775100 775140	---	XVDRIVER	No
OG	LK11	Float	2	8	Float	8	OGDRIVER	No
XM	DMC11	Float	2	8	Float	8	XMDRIVER	Yes
TTA	DZ11	Float	2	8	Float	8	DZDRIVER	Yes
XK	KMC11	Float	2	8	Float	8	XKDRIVER	No
OH	LPP11	Float	2	8	Float	8	OHDRIVER	No
OI	VMV21	Float	2	8	Float	8	OIDRIVER	No
OJ	VMV31	Float	2	8	Float	16	OJDRIVER	No
OK	DWR70	Float	2	8	Float	8	OKDRIVER	No
DL	RL11	Float	1	4	Float	8	DLDRIVER	Yes
MS	TS11	Float	1	4	772524 772530 772534	---	TSDRIVER	Yes
LA	LPA11	Float	2	8	770460	---	LADRIVER	Yes
LA	LPA11	Float	2	8	Float	16	LADRIVER	Yes
OL	KW11C	Float	2	8	Float	8	OLDRIVER	No
DY	RX211	Float	1	4	Float	8	DYDRIVER	Yes
XA	DR11W	Float	1	4	Float	8	XADRIVER	Yes
XB	DR11B	124	---	---	772410	---	XBDRIVER	No
XB	DR11B	Float	1	4	772430	---	XBDRIVER	No
XB	DR11B	Float	1	4	Float	8	XBDRIVER	No
XD	DMP11	Float	2	8	Float	8	XDDRIVER	Yes
ON	DPV11	Float	2	8	Float	8	ONDRIVER	No
IS	ISB11	Float	2	8	Float	8	ISDRIVER	No
XD	DMV11	Float	2	8	Float	16	XDDRIVER	No
XE	UNA	Float	1	4	Float	8	XEDRIVER	No
XQ	QNA	Float	1	4	774460	---	XQDRIVER	Yes
PU	UDA	Float	1	4	Float	4	PUDRIVER	Yes
XS	KMS11	Float	3	8	Float	16	XSDRIVER	No
XP	PCL11	Float	2	8	764200 764240 764300 764340	---	XPDRIVER	No
VB	VS100	Float	1	4	Float	16	VBDRIVER	No
PT	TU81	Float	1	4	Float	4	PUDRIVER	Yes
OQ	KMV11	Float	2	8	Float	16	OQDRIVER	No
UK	KCT32	Float	2	8	764400 764440 764500 764540	---	UKDRIVER	No
IX	IEQ11	Float	2	8	764100	---	IXDRIVER	No
TX	DHV11	Float	2	8	Float	16	YFDRIVER	Yes
DT	TC11	214	1	---	777340	---	DTDRIVER	No
VC	VCB01	Float	2	1	777200	---	VCDRIVER	Yes
VC	VCB01	Float	2	1	Float	64	VCDRIVER	Yes
OT	LNV11	Float	1	4	776200	---	OTDRIVER	No
LD	LNV21	Float	1	4	Float	16	LDDRIVER	No
ZQ	QTA	Float	1	4	772570	---	ZQDRIVER	No
ZQ	QTA	Float	1	4	Float	8	ZQDRIVER	No
SJ	DSV11	Float	1	4	Float	8	SJDRIVER	No
OU	ADV11C	Float	2	8	Float	8	OUDRIVER	No
OV	AAV11	Float	0	8	770440	---	OVDRIVER	No
OV	AAV11C	Float	0	8	Float	8	OVDRIVER	No
AX	AXV11C	140	2	---	776400	---	AXDRIVER	No
AX	AXV11C	Float	2	8	Float	8	AXDRIVER	No
KZ	KWV11C	Float	2	8	770420	---	KZDRIVER	No
KZ	KWV11C	Float	2	8	Float	4	KZDRIVER	No
AZ	ADV11D	Float	2	8	776410	---	AZDRIVER	No
AZ	ADV11D	Float	2	8	Float	4	AZDRIVER	No
AY	AAV11D	Float	2	8	776420	---	AYDRIVER	No
AY	AAV11D	Float	2	8	Float	4	AYDRIVER	No
VA	VCB02	Float	3	16	777400 777402 777404 777406 . . . 8 units maximum	---	VADRIVER	Yes
DN	DRV11J	Float	16	4	764160 764140 764120	---	DNDRIVER	No
HX	DRQ3B	Float	2	8	Float	16	HXDRIVER	No
VQ	VSV24	Float	1	4	Float	8	VQDRIVER	No
VV	VSV21	Float	1	4	Float	8	VVDRIVER	No
BQ	IBQ01	Float	1	4	Float	8	BQDRIVER	No
UT	MIRA	Float	2	8	Float	8	UTDRIVER	No
IX	IEQ11	Float	2	8	Float	16	IXDRIVER	No
AW	ADQ32	Float	2	8	Float	32	AWDRIVER	No
VX	DTC04	Float	2	8	Float	2	VXDRIVER	No
CQ	DESNA	Float	1	4	Float	32	CQDRIVER	No
GQ	IGQ11	Float	2	8	Float	4	GQDRIVER	No

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