Updated: 11 December 1998

OpenVMS System Services Reference Manual

If you do not specify this quota and the created process is a detached process, the detached process receives a default value of 0, that is, unlimited CPU time.

If you do not specify this quota and the created process is a subprocess, the subprocess receives half the CPU time limit quota of the creating process.

If you specify this quota as 0, the created process has unlimited CPU time, provided the creating process also has unlimited CPU time. If, however, the creating process does not have unlimited CPU time, the created process receives half the CPU time limit quota of the creating process.

The CPU time limit quota is a consumable quota; that is, the amount of CPU time used by the created process is not returned to the creating process when the created process is deleted.

• Minimum: PQL_MCPULM
• Default: PQL_DCPULM
• Deductible

PQL$_DIOLM

• Minimum: PQL_MDIOLM
• Default: PQL_DDIOLM
• Nondeductible

PQL$_ENQLM

• Minimum: PQL_MENQLM
• Default: PQL_DENQLM
• Pooled

PQL$_FILLM

• Minimum: PQL_MFILLM
• Default: PQL_DFILLM
• Pooled

PQL$_JTQUOTA

• Minimum: PQL_MJTQUOTA
• Default: PQL_DJTQUOTA
• Nondeductible

PQL$_PGFLQUOTA

• Minimum: PQL_MPGFLQUOTA
• Default: PQL_DPGFLQUOTA
• Pooled

PQL$_PRCLM

• Minimum: PQL_MPRCLM
• Default: PQL_DPRCLM
• Pooled

PQL$_TQELM

• Minimum: PQL_MTQELM
• Default: PQL_DTQELM
• Pooled

PQL$_WSDEFAULT

• Minimum: PQL_MWSDEFAULT
• Default: PQL_DWSDEFAULT
• Nondeductible

PQL$_WSEXTENT

• Minimum: PQL_MWSEXTENT
• Default: PQL_DWSEXTENT
• Nondeductible

PQL$_WSQUOTA

• Minimum: PQL_MWSQUOTA
• Default: PQL_DWSQUOTA
• Nondeductible

Use of the Quota List

The values specified in the quota list are not necessarily the quotas that are actually assigned to the created process. The $CREPRC service performs the following steps to determine the quota values that are assigned when you create a process on the same node:

1. It constructs a default quota list for the process being created, assigning it the default values for all quotas. Default values are SYSGEN parameters and so might vary from system to system.
2. It reads the specified quota list, if any, and updates the corresponding items in the default list. If the quota list contains multiple entries for a quota, only the last specification is used.
3. For each item in the updated quota list, it compares the quota value with the minimum value required (also a SYSGEN parameter) and uses the larger value. Then, the following occurs:
   • If a subprocess is being created or if a detached process is being created and the creating process does not have IMPERSONATE or CMKRNL privilege, the resulting value is compared with the current value of the corresponding quota of the creating process and the lesser value is used.
     Then, if the quota is a deductible quota, that value is deducted from the creating process's quota, and a check is performed to ensure that the creating process will still have at least the minimum quota required. If not, the condition value SS$_EXQUOTA is returned and the subprocess or detached process is not created.
     Pooled quota values are ignored.
   • If a detached process is being created and the creating process has IMPERSONATE or CMKRNL privilege, the resulting value is not compared with the current value of the corresponding quota of the creating process and the resulting value is not deducted from the creating process's quota. A process with IMPERSONATE or CMKRNL privilege is allowed to create a detached process with quota values larger than it has.

When you create a detached process on another OpenVMS Cluster node, the quotas assigned to the process are determined in the following way:

1. The $CREPRC service reads the specified quota list, if any. If it contains multiple entries for a quota, only the last specification is used. If the process does not have IMPERSONATE or CMKRNL privilege, the service compares each value in the list with the current value of the corresponding quota of the creating process and uses the lesser value. It sends the resulting quota list to the node on which the new process is to be created.
2. On that node, the $CREPRC service constructs a default quota list for the process being created, assigning it default values for all quotas based on that node's SYSGEN parameters.
3. It updates the default list with the corresponding values from the quota list.
4. For each item in the updated quota list, it compares the quota value with the minimum value required based on that node's SYSGEN parameters and uses the larger value.

prcnam

If a subprocess is being created, the process name is implicitly qualified by the UIC group number of the creating process. If a detached process is being created, the process name is qualified by the group number specified in the uic argument.

baspri

If you want a created process to have a higher priority than its creating process, you must have ALTPRI privilege to raise the priority level. If the caller does not have this privilege, the specified base priority is compared with the caller's priority and the lower of the two values is used. A process with ALTPRI privilege running on a VAX node can create a process with a priority greater than 31 on an Alpha node.

If the baspri argument is not specified, the priority defaults to 2 for VAX MACRO and VAX BLISS--32 and to 0 for all other languages.

uic

If you do not specify the uic argument or specify it as 0 (the default), $CREPRC creates a process and assigns it the UIC of the creating process.

If you specify a nonzero value for the uic argument, $CREPRC creates a detached process. This value is interpreted as a 32-bit octal number, with two 16-bit fields:

• bits 0--15---member number
• bits 16--31---group number

You need IMPERSONATE or CMKRNL privilege to create a detached process with a UIC that is different from the UIC of the creating process.

If the image argument specifies the SYS$SYSTEM:LOGINOUT.EXE, the UIC of the created process will be the UIC of the caller of $CREPRC, and the UIC parameter is ignored.

mbxunt

If you do not specify the mbxunt argument or specify it as 0 (the default), the operating system sends no termination message when it deletes the process.

The Get Device/Volume Information ($GETDVI) service can be used to obtain the unit number of the mailbox.

If you specify the mbxunt argument, the mailbox is used when the created process actually terminates. At that time, the $ASSIGN service is issued for the mailbox in the context of the terminating process and an accounting message is sent to the mailbox. If the mailbox no longer exists, cannot be assigned, or is full, the error is treated as if no mailbox had been specified.

If you specify this argument when you create a process on another node, an accounting message will be written to the mailbox when the process terminates. If the node is removed from the cluster before the created process terminates, an accounting message will be simulated. The simulated message will contain the created process's PID and name and a final status of SS$_NODELEAVE, but will lack execution statistics.

Note that two processes on different nodes cannot use the termination mailbox for general interprocess communication.

The accounting message is sent before process rundown is initiated but after the process name has been set to null. Thus, a significant interval of time can occur between the sending of the accounting message and the final deletion of the process.

To receive the accounting message, the caller must issue a read to the mailbox. When the I/O completes, the second longword of the I/O status block, if one is specified, contains the process identification of the deleted process.

The $ACCDEF macro defines symbolic names for offsets of fields within the accounting message. The offsets, their symbolic names, and the contents of each field are shown in the following table. Unless stated otherwise, the length of the field is 4 bytes.

Offset	Symbolic Name	Contents
0	ACC$W_MSGTYP	MSG$_DELPROC (2 bytes)
2		Not used (2 bytes)
4	ACC$L_FINALSTS	Exit status code
8	ACC$L_PID	External process identification
12		Not used (4 bytes)
16	ACC$Q_TERMTIME	Current time in system format at process termination (8 bytes)
24	ACC$T_ACCOUNT	Account name for process, blank filled (8 bytes)
32	ACC$T_USERNAME	User name, blank filled (12 bytes)
44	ACC$L_CPUTIM	CPU time used by the process, in 10-millisecond units
48	ACC$L_PAGEFLTS	Number of page faults incurred by the process
52	ACC$L_PGFLPEAK	Peak paging file usage
56	ACC$L_WSPEAK	Peak working set size
60	ACC$L_BIOCNT	Count of buffered I/O operations performed by the process
64	ACC$L_DIOCNT	Count of direct I/O operations performed by the process
68	ACC$L_VOLUMES	Count of volumes mounted by the process
72	ACC$Q_LOGIN	Time, in system format, that process logged in (8 bytes)
80	ACC$L_OWNER	Process identification of owner

The length of the termination message is equated to the constant ACC$K_TERMLEN.

stsflg

Each option (bit) has a symbolic name, which the $PRCDEF macro defines. You construct the stsflg argument by performing a logical OR operation using the symbolic names of each desired option. The following table describes the symbolic name of each option.

Symbolic Name	Description
PRC$M_BATCH	Create a batch process. IMPERSONATE privilege is required.
PRC$M_IMPERSONATE	Create a detached process under another UIC.
PRC$M_DISAWS	Disable system-initiated working set adjustment.
PRC$M_HIBER	Force process to hibernate before it executes the image.
PRC$M_IMGDMP	Enable image dump facility. If an image terminates due to an unhandled condition, the image dump facility writes the contents of the address space to a file in your current default directory. The file name is the same as the name of the terminated image. The file type is .DMP.
PRC$M_INTER	Create an interactive process. This option is meaningful only if the image argument specifies SYS$SYSTEM:LOGINOUT.EXE. The purpose of this option is to provide you with information about the process. When you specify this option, it identifies the process as one that is in communication with another user (an interactive process). For example, if you use the DCL lexical function F$MODE to make an inquiry about a process that has specified the PRC$M_INTER option, F$MODE returns the value INTERACTIVE.
PRC$M_NETWRK	Create a process that is a network connect object. IMPERSONATE privilege required.
PRC$M_NOACNT	Do not perform accounting. ACNT privilege is required.
PRC$M_NOPASSWORD	Do not display the Username: and Password: prompts if the process is interactive and detached and the image is SYS$SYSTEM:LOGINOUT.EXE. If you specify this option in your call to $CREPRC, the process created by the call is logged in under the user name associated with the creating process. If you do not specify this option for an interactive process, SYS$SYSTEM:LOGINOUT.EXE prompts you for the user name and password to be associated with the process. The prompts are displayed at the SYS$INPUT device.
PRC$M_NOUAF	Do not check authorization file if the process is detached and the image is SYS$SYSTEM:LOGINOUT.EXE. You should not specify this option if a subprocess is being created. In previous versions of the operating system, the symbolic name of this option was PRC$M_LOGIN. The symbolic name has been changed to more accurately denote the effect of setting this bit. For compatibility with existing user programs, you can still specify this bit as PRC$M_LOGIN.
PRC$M_PARSE_EXPANDED	Sets the PARSE_STYLE_PERM and the PARSE_STYLE_IMAGE properties for the new process to EXTENDED.
PRC$M_PSWAPM	Inhibit process swapping. PSWAPM privilege is required.
PRC$M_SSFEXCU	Enable system service failure exception mode.
PRC$M_SSRWAIT	Disable resource wait mode.
PRC$M_SUBSYSTEM	Inherit any protected subsystem identifiers. The default is that the new process does not inherit subsystem identifiers.
PRC$M_TCB	Mark a process as part of the trusted computing base (TCB). As such, it is expected to perform its own auditing. IMPERSONATE privilege is required.

Note that options PRC$M_BATCH, PRC$M_INTER, PRC$M_NOUAF, PRC$M_NETWRK, and PRC$M_NOPASSWORD are intended for use by Compaq software.

itmlst

node

Description

The Create Process service creates a subprocess or detached process on behalf of the calling process. A subprocess can be created only on the current OpenVMS Cluster node. A detached process can be created on the current OpenVMS Cluster node or on the node specified with the node argument.

A detached process is a fully independent process. For example, the process that the system creates when you log in is a detached process. A subprocess, on the other hand, is related to its creating process in a treelike structure; it receives a portion of the creating process's resource quotas and must terminate before the creating process. Any subprocesses that still exist when their creator is being deleted are automatically deleted.

The presence of the uic argument, node argument, or the PRC$M_IMPERSONATE flag specifies that the created process is detached.

Creating a process is synchronous in that the process has actually been created and its PID determined before control returns to the program that requested the system service. Note, however, that the new process has not necessarily begun to execute at that point. Some error conditions are not detected until the created process executes. These conditions include an invalid or nonexistent image; invalid SYS$INPUT, SYS$OUTPUT, or SYS$ERROR logical name equivalence; inadequate quotas; or insufficient privilege to execute the requested image.

In creating a detached or subprocess, you can specify that the process run the image SYS$SYSTEM:LOGINOUT.EXE. During interactive logins, LOGINOUT performs the following functions:

1. It validates user name and password.
2. It reads the system authorization file record associated with that user and redefines the process environment based on information from the record.
3. It maps a command language interpreter (CLI) into the process and passes control to it.

The CLI reads a command from SYS$INPUT, processes it, and reads another command. The presence of the CLI enables the process to execute multiple images. It also enables an image running in the process to use Run-Time Library procedures, such as LIB$SPAWN, LIB$DO_COMMAND, and LIB$SET_LOGICAL, that require a CLI.

Running in the context of a process you create through $CREPRC, LOGINOUT can perform some or all of the preceding steps, depending on whether the process is a subprocess or a detached process and on the values of PRC$M_NOPASSWORD and PRC$M_NOUAF in the stsflg argument.

Certain characteristics of a created process can be specified explicitly through $CREPRC system service arguments, while other characteristics are propagated implicitly from the $CREPRC caller. Implicit characteristics include the following:

• Current default directory
• Creator's equivalence name for SYS$DISK
• User and account names
• Command language interpreter (CLI) name and command table file name

Note, however, that after the process has been created, if it runs LOGINOUT and LOGINOUT redefines the process environment, those characteristics will be overridden by information from the system authorization file.

Several process characteristics are relevant to the creation of a process on another OpenVMS Cluster node, in particular, process quotas, default directory, SYS$DISK equivalence name, CLI name, and CLI command table name.

Quotas for a process created on another OpenVMS Cluster node are calculated as previously described in the section on the use of the quota list; namely, they are based on explicit values passed by the creator and SYSGEN parameters on the other OpenVMS Cluster node. If the other node has its own authorization file with node-specific quotas, you might want to specify in the $CREPRC request that the process run LOGINOUT so it can redefine the process environment based on that node's quotas for the user.

Unless overridden by LOGINOUT, the new process will use its creator's default disk and directory. If the disk is not mounted clusterwide, the created process might need to redefine SYS$DISK with an equivalence name that specifies a disk accessible from that node.

When you set the PRC$M_NOUAF flag in the stsflg argument and create a process running LOGINOUT, LOGINOUT will attempt to map a CLI and command table with the same file names as those running in your process. The CLI and command table images must therefore have already been installed by the system manager on the other node. Problems can arise when you are using something other than the DCL CLI and its standard command tables. For example, if you are running on a VAX node with MCR as your current CLI, LOGINOUT will be unable to map that CLI on an Alpha node. The new process will be created but then aborted by LOGINOUT.

A detached process is considered an interactive process only if (1) the process is created with the PRC$M_INTER option specified and (2) SYS$INPUT is not defined as a file-oriented device.

The $CREPRC service requires system dynamic memory.

Required Access or Privileges

The calling process must have the following:

• IMPERSONATE or CMKRNL privilege to create any of the following types of process:
  • A detached process with a UIC that is different from the UIC of the calling process
  • A detached process with a larger value specified for some quota than is authorized for the caller
  • A detached process on another node if the SYSGEN parameter CWCREPRC_ENABLE has a value of 0
• IMPERSONATE privilege to create any of the following types of process:
  • A batch process
  • A network process
  • A trusted computing base process
• ALTPRI privilege to create a subprocess with a higher base priority than the calling process
• SETPRV privilege to create a process with privileges that the calling process does not have
• PSWAPM privilege to create a process with process swap mode disabled
• ACNT privilege to create a process with accounting functions disabled
• OPER privilege to create a detached process on another OpenVMS Cluster node on which interactive logins have not yet been enabled

Required Quota

The number of subprocesses that a process can create is controlled by the subprocess (PRCLM) quota; this quota is returned when a subprocess is deleted.

The number of detached processes on any one OpenVMS Cluster node that a process can create with the same user name is controlled by the MAXDETACH entry in the user authorization file (UAF).

When a subprocess is created, the value of any deductible quota is subtracted from the total value the creating process has available, and when the subprocess is deleted, the unused portion of any deductible quota is added back to the total available to the creating process. Any pooled quota value is shared by the creating process and all its subprocesses.

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