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Using INSTALL to Install Known Images  



The Install utility (INSTALL) stores information about images in memory. Use INSTALL for the following reasons:

Reason For More Information
To conserve memory use for images that are used concurrently
Installing Images to Conserve Physical Memory
To improve system performance
Installing Images to Improve Image Activation Performance
On Alpha and I64 systems, to improve performance by using images with shared address data1
Installing Images with Shared Address Data
To make executable images that require enhanced privileges available for general use
Privileged Executable Images
To allow a nonprivileged image to call the privileged functions of a shareable image
Privileged Shareable Images
To mark a shareable image as trusted so it can be invoked by privileged executable images
Activating Images in a Privileged Context

The site-independent startup command procedure, STARTUP.COM, uses INSTALL to install certain system images when the system boots. You use INSTALL to install other selected images, according to the needs of your site.

Installed images must be reinstalled each time the system reboots. To do so, include INSTALL commands in the site-specific startup command procedure SYSTARTUP_VMS.COM, as explained in the HP OpenVMS System Manager's Manual, Volume 1: Essentials.

The Install utility (INSTALL) only installs images that are linked with the /NOTRACEBACK qualifier.

Note that INSTALL commands perform a different function than System Generation utility (SYSGEN) INSTALL commands.

The following sections explain installed images and how to use the Install utility.

Understanding Images and Known Images  

An image is a collection of procedures and data bound together by the Linker utility. Executable images can be executed (or run) in a process, either by a command line interpreter (CLI) or the $CREPRC system service. Usually, executable programs have the file type .EXE.

There are three types of images:

Image Type Description
Executable
An image linked with the /EXECUTABLE qualifier (or without the /SHAREABLE qualifier) of the Linker utility. For more information, refer to the HP OpenVMS Linker Utility Manual.
Shareable
An image linked with the /SHAREABLE qualifier of the Linker utility. Shareable images are sometimes referred to as linkable images because they can be specified--implicitly or explicitly--as input files to the link of another file. A shareable image is not copied into the executable images that link with it. Thus, only one copy of the shareable image needs to be on disk, no matter how many executable images have linked with it. For more information, refer to the HP OpenVMS Linker Utility Manual.
System
An image that does not run under the control of the operating system. It is intended for standalone operation only. The content and format of a system image differs from that of shareable images and executable images. For more information, refer to the HP OpenVMS Linker Utility Manual.

When you install an image with INSTALL, the image is assigned attributes and becomes known to the system. For this reason, an installed image is also called a known image.

The image activator processes search lists in two passes, in order to favor known images. On its first pass through the search list, the image activator looks up images as known files. If needed, on a second pass through the search list, the image activator looks up images on disk.

Understanding Known File Entries  

The system defines known images in internal data structures called known file entries. Each entry identifies the file name of the installed image and the attributes with which it was installed (for information about attributes of installed images, see Understanding Attributes You Can Assign to Known Images).

Known file entries last only while the system is operating. If the system is shut down or fails for any reason, you must reinstall all known images after the system is rebooted.

Understanding Attributes You Can Assign to Known Images  

By specifying appropriate qualifiers to INSTALL commands, you can assign attributes to known images. Attributes of Known Images describes these attributes and the qualifiers that are used to assign them to known images.

Table 2   Attributes of Known Images
Attribute Description Qualifier
Header resident
The header of the image file (native images only) remains permanently resident, saving one disk I/O operation per file access. For images with single-block file headers, the cost is less than 512 bytes of paged dynamic memory per file; for images with multiblock headers, the cost varies according to the header block count. Images installed header resident are implicitly installed permanently open.
/[NO]HEADER_RESIDENT
Permanently open
The image file remains open, so access to the image does not require a call to the file system.
/OPEN
Privileged
Amplified privileges are temporarily assigned to any process running the image, permitting the process to exceed its user authorization file (UAF) privilege restrictions during execution of the image. In this way, users with normal privileges can run programs that require higher-than-normal privileges. This attribute (and the /PRIVILEGED qualifier that creates it) applies only to executable images.
/PRIVILEGED[=(priv-name[,...])]
Protected
When the image is activated, the address space for the image is protected against modification by user-mode code. This is critical for shareable code that runs in kernel or executive mode.
/PROTECTED
Resident2
On Alpha and I64 systems, code or read-only data for an image is made permanently resident in a system region of memory. This improves performance by using a special page mapping to reduce translation buffer (TB) miss rates. The resident attribute applies to shareable or executable images that have been linked with the qualifier /SECTION_BINDING=(CODE,DATA).
/RESIDENT
Shared
More than one user can access the read-only and non-copy-on-reference read/write sections of the image concurrently, so that only one copy of those sections needs to be in physical memory. (Copy-on-reference sections always require a separate copy for each process.) The image is implicitly declared permanently open.
/SHARED
Writable
When a shareable non-copy-on-reference writable section is removed from physical memory (for paging reasons or because no processes are referencing it), it is written back to the image file. Any updates made by processes mapped to the section, therefore, are preserved (while the initial values are lost). The image must also be declared shareable.
/WRITABLE

Determining Which Images to Install  

You can install images for the following reasons:

Because an installed file requires system resources, such as paged dynamic memory, install those files that most improve system performance and site requirements. The INSTALL command LIST provides information about installed images to help you evaluate the merits of installing images. For example, the LIST command calculates the number of times each image is accessed, and shows the number of concurrent accesses, so you can determine if the installation of the images is worth the overhead.

Installing Images to Improve Image Activation Performance  

You can improve image activation performance by installing images that run frequently. Image activation performance improves when programs are installed because the operating system opens installed files by file ID rather than by file name, thus eliminating costly directory operations.

Installing images as header resident further enhances activation performance because the system avoids the overhead of I/O operations to read the image header into memory.

To install an image as header resident, specify the /HEADER_RESIDENT qualifier when you install the image. This makes the header of the image file remain permanently resident, saving disk I/O. Specifying the /HEADER_RESIDENT qualifier implicitly makes the images permanently open.

Image headers are stored in paged dynamic memory. The size of the image headers varies.

Frequently accessed images, critical to a site's operations, can be installed as open images. To install an image as permanently open, specify the /OPEN qualifier when you install the image. The image file remains open, so access to the image does not require a call to the file system. The cost of keeping an image file permanently open is approximately 512 bytes of nonpaged dynamic memory per file.

Installing Images with Shared Address Data  

Using shared address data on OpenVMS Alpha and I64 systems improves performance at the following times:

For details, refer to the INSTALL section of the HP OpenVMS System Management Utilities Reference Manual.

Related Terms

Explanations of terms related to shared address data follow.

System-Provided Images  

Many images that are part of the OpenVMS software product are installed as shared known images with shared address data. This provides the performance benefit without requiring the system manager to take any explicit action.

Application Images  

As system manager, you might choose to install additional images with shared address data. In considering this option, you need to investigate application dependencies on shareable images.

Installing Images to Conserve Physical Memory  

You can conserve physical memory by installing images that usually run concurrently from several processes. When an image is not installed, or is installed without the shared attribute, each process running the image requires private sections in memory. Shared images conserve physical memory because only one copy of the code needs to be in memory at any time, and many users can access the code concurrently. Use the /SHARED qualifier to install images as shared images.

When you install an image with the shared attribute, permanent system global sections are created. Execution of non-copy-on-reference global sections requires only one copy per section to be in physical memory, no matter how many processes are running the image to which the sections belong.

The number of images you can install with the shared attribute is restricted by the GBLPAGES and GBLSECTIONS system parameters. For more information about these system parameters, refer to the HP OpenVMS System Management Utilities Reference Manual.

Installing Images to Enhance Privileges of Images 

There are two ways to allow an image to execute in an enhanced privilege environment:

Privileged Executable Images  

A nonprivileged process can perform the privileged functions of an executable image when the image is installed with privileges. Install executable images with enhanced privileges by using the /PRIVILEGED qualifier; amplified privileges are temporarily assigned to any process running the image (executable images only), permitting the process to exceed its user authorization file (UAF) privilege restrictions during execution of the image. In this way, users with normal privileges can run programs that require higher-than-normal privileges.

For an image installed with privileges to activate another image, such as a shareable image, either by having it linked to the privileged image or by using LIB$FIND_IMAGE_SYMBOL, the following conditions hold:

Privileged Shareable Images  

A privileged shareable image is a shareable image with defined entry points that execute in inner (executive or kernel) mode. Inner-mode entry points in shareable images are referred to as user-written system services.

To create a privileged shareable image, you must:

  1. Create a program section with the VECTOR attribute containing a PLV (privileged library vector) data structure.
  2. Link the shareable image with the /PROTECT command qualifier or the PROTECT= option of the Linker utility, so that the image acquires its particular form of enhanced privileges.
  3. Install the privileged shareable image with the Install utility, specifying both the /PROTECTED and the /SHARED qualifiers. The /PROTECTED qualifier assigns the protected attribute. The /SHARED qualifier assigns the shareable attribute. See Understanding Attributes You Can Assign to Known Images for information about these attributes.

NoteYou cannot grant privileges to a shareable image using the /PRIVILEGED qualifier for the INSTALL commands ADD or CREATE. This qualifier works only for executable images.

For more information about creating privileged shareable images, refer to HP OpenVMS Programming Concepts.

Activating Images in a Privileged Context  

When a process performs one of the following actions, the image activator enters a restricted mode of operation similar to that entered when a privileged program is run:

In this mode of operation:


NoteThe executable image that calls an execute-only shareable image must be installed with the /EXECUTE_ONLY qualifier, which enables the executable image to activate shareable images to which the process has execute but not read access.

The /EXECUTE_ONLY qualifier has meaning only for executable images.

This restriction assures that shareable images running in a privileged context can be trusted to behave as expected.


Specifying File Names in INSTALL  

When you use INSTALL commands, your file specifications must name existing executable or shareable images. OpenVMS RMS resolves each file specification using the following defaults:

You can specify a specific version of the file as the known version of the image with the CREATE or REPLACE command. Even if other versions of the file exist, the version that you specify will be the version that satisfies all known file lookups for the image.

Installing Images with INSTALL  

Before performing this task, you should understand the following points:

How to Perform This Task

  1. Give yourself the CMKRNL privilege by entering the following command:
    $ SET PROCESS/PRIVILEGES=CMKRNL
  2. Invoke INSTALL by entering the following command:
    $ INSTALL
  3. Enter the CREATE command in the following format:CREATE file-spec [/qualifier...]Specify one or more of the following qualifiers, depending on which attributes you want to assign to the image: For more information about installing images, refer to the INSTALL command CREATE in the HP OpenVMS System Management Utilities Reference Manual.

NoteInstalling the Install utility itself requires that a number of shareable images have been previously installed. If any of those required shareable images (such as SMG$SHR, LIBOTS, and so on) is unavailable, the execution of the Install utility fails. Since INSTALL will not work in this situation, you cannot simply install the missing images. To work around this problem, redefine the INSTALL command as follows:
$ DEFINE INSTALL SYS$SYSTEM:INSTALL.EXE;0
When you now enter the INSTALL command, the image activator does not check the known files list for INSTALL.EXE, and the INSTALL command will complete, allowing you to install the required shareable images.

Displaying Known Images with INSTALL  

Use the INSTALL command LIST to display information about known images.

The information displayed with the /FULL qualifier of the LIST command can help you determine if installing an image is worth the expense.

How to Perform This Task

  1. Invoke INSTALL by entering the following command:
    $ INSTALL
  2. To display a list of all known images and their attributes, enter the LIST command. To display attributes for a specific image, specify the name of the image as follows:LIST file-specFor example:
    INSTALL> LIST LOGINOUT
  3. To display complete information about a specific image, including the number of accesses, the number of concurrent accesses, and the number of global sections created, specify the /FULL qualifier as follows:LIST/FULL file-spec

Example

The following example displays complete information about the installed image LOGINOUT.EXE, including the number of accesses, the number of concurrent accesses, and the number of global sections created:

$ INSTALL
INSTALL> LIST/FULL LOGINOUT

DISK$VMS551:<SYS2.SYSCOMMON.SYSEXE>.EXE
   LOGINOUT;2       Open Hdr Shar Prv 
        Entry access count         = 36366
        Current / Maximum shared   = 1 / 10
        Global section count       = 3
        Privileges = CMKRNL SYSNAM LOG_IO ALTPRI TMPMBX SYSPRV 
INSTALL> 

Defining Logical Names for Shareable Image Files 

If a shareable image is not located in SYS$SHARE, you must define a logical name for that image in order to run an executable image linked against it. For example, if the file specification for STATSHR is SYS$SHARE:STATSHR.EXE, no logical name is necessary. But if you put STATSHR in SYS$DEVICE:[TEST], you must define STATSHR as a logical name before running an executable image that calls it. The logical name must be the same one that was used as the input file specification for the shareable image when it was linked (this is the same name used in installation). For example:

$ DEFINE STATSHR SYS$SYSDEVICE:[TEST]STATSHR
By redefining the logical name of a shareable image, you can replace that shareable image with another without requiring the calling executable image to relink. For example, the following statement redefines the file name STATSHR. It becomes the logical name of the shareable image SYS$SYSDEVICE:[MAIN]STATSHR.EXE for executable images calling STATSHR.
$ DEFINE STATSHR SYS$SYSDEVICE:[MAIN]STATSHR

NoteLogical names defined in the process or group logical name table are ignored when you run a privileged executable image. Only logical names and table names defined in executive or kernel modes are used to find the image.

Removing Known Images  

The INSTALL command REMOVE removes a known file entry for an image and deletes any global sections created when the image was installed. Note that a volume cannot be dismounted while any known file entries are associated with it. To dismount a volume, you must delete all known images associated with it. You must also wait for all processes using those images to exit. Use the DCL command SHOW DEVICES/FILES to determine the status of the files.

For more information about the INSTALL command DELETE, refer to the INSTALL section of the HP OpenVMS System Management Utilities Reference Manual.


Footnotes
1Alpha or I64 specific
2Alpha and I64 specific

( Number takes you back )


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