Document revision date: 15 July 2002

The default action for LIBDECOMP.COM is the expand function. You can explicitly specify EXPAND as the first parameter on your command line, but this is not necessary. Unless the first parameter is LIST or REDUCE, the expand function is used by default.

If the expand function is used, the remaining parameters specify which of the libraries to expand. You can specify ALL to expand all libraries known to the utility, or you can specify up to eight library names (seven names if EXPAND is specified). Wildcard characters are not permitted. The specified libraries must be known to the utility. (To expand any other libraries, you must use the LIBRARY command, as described in Section 17.9.3.) If you do not specify ALL or a list of libraries, LIBDECOMP.COM prompts you for the libraries to expand. You can specify any number of libraries in response to the prompt.

The expand function produces a display similar to the one shown in the following OpenVMS Alpha example. After the header lines are displayed, there is a pause while LIBDECOMP.COM checks the status of each library.

OpenVMS Library Decompression Utility Candidate Libraries to be expanded (Libraries not present and libraries already expanded are not listed) 1 ACLEDT.HLB 13 NCPHELP.HLB 25 VAXCRTLD.OLB 2 BKM$HELP.HLB 14 SDA.HLB 26 VAXCRTLDX.OLB 3 DBG$HELP.HLB 15 SHWCLHELP.HLB 27 VAXCRTLT.OLB 4 DBG$UIHELP.HLB 16 SYSGEN.HLB 28 VAXCRTLTX.OLB 5 EDTHELP.HLB 17 SYSMANHELP.HLB 29 VAXCRTLX.OLB 6 EVE$HELP.HLB 18 TPUHELP.HLB 30 ERFLIB.TLB 7 EVE$KEYHELP.HLB 19 UAFHELP.HLB 31 LIB_ADA_SUBSET.TLB 8 EXCHNGHLP.HLB 20 LANIDEF.MLB 32 NTA.TLB 9 HELPLIB.HLB 21 LIB.MLB 33 STARLETSD.TLB 10 LANCP$HELP.HLB 22 STARLET.MLB 34 SYS$LIB_C.TLB 11 LATCP$HELP.HLB 23 STARLET.OLB 35 SYS$STARLET_C.TLB 12 MAILHELP.HLB 24 VAXCRTL.OLB 36 VMS$VOLATILE_PRIVATE_INTERFACES.OLB 37 STARLET_RECENT_ADA_SUBSET.TLB A ALL libraries to be expanded H Display HELP information for LIBDECOMP E EXIT this procedure

If you specified ALL, the following message is displayed, and the utility then expands all listed libraries.

"ALL" specified; all libraries will be processed

If you did not specify ALL, you are prompted as follows:

* Enter a letter or the number(s) of libraries to be expanded (Separate multiple numbers with a comma)

Enter A, H, E, or one or more numbers to indicate which libraries to expand. There is no limit to how many numbers you can specify.

If you enter parameters to identify specific libraries to expand, LIBDECOMP.COM does not display the list as shown in the example; rather, it lists each library as it is processed.

Examples

• Either of the following commands expands all libraries:

  $ @SYS$UPDATE:LIBDECOMP ALL $ @SYS$UPDATE:LIBDECOMP EXPAND ALL

• To choose whether to expand some or all of the libraries in a menu, first enter one of the following commands:

  $ @SYS$UPDATE:LIBDECOMP $ @SYS$UPDATE:LIBDECOMP EXPAND

  
  Then, as shown in an earlier example, you are prompted to specify all libraries or to specify the numbers for an unlimited number of individual libraries to be expanded.

• To bypass the menu and expand only selected libraries, enter a command similar to one of the following, in which you specify the library names in the command line instead of responding to a prompt:

  $ @SYS$UPDATE:LIBDECOMP HELPLIB.HLB STARLET.MLB LIB.MLB $ @SYS$UPDATE:LIBDECOMP EXPAND HELPLIB STARLET.MLB LIB

  
  Both commands have the same result: to expand the HELPLIB.HLB, STARLET.MLB, and LIB.MLB libraries.

When you specify REDUCE as the first parameter in your command line, LIBDECOMP.COM reduces libraries that have been expanded.

You can specify ALL after REDUCE to reduce all of the libraries known to the utility, or you can specify a list of up to seven libraries. Wildcard characters are not permitted.

If you do not specify ALL or the name of at least one library, LIBDECOMP.COM prompts you for the libraries to reduce. There is no limit to the number of libraries you can list in response to the prompt.

The reduce function produces a display similar to that of the expand function except that it displays only the libraries eligible to be reduced.

Examples

• The following command reduces all libraries that have been expanded:

  $ @SYS$UPDATE:LIBDECOMP REDUCE ALL

• To choose whether to reduce some or all of the libraries in a menu, first enter the following command:

  $ @SYS$UPDATE:LIBDECOMP REDUCE

  
  Then, as with the expand function, you are prompted to specify all libraries or to specify the numbers for an unlimited number of individual libraries to be reduced.

You can submit the Library Decompression utility to a batch queue by using the DCL command SUBMIT with the /PARAMETERS qualifier, as follows:

SUBMIT SYS$UPDATE:LIBDECOMP /PARAMETERS=(p1[,p2,...])

The batch procedure produces the same results as the interactive procedure, but with the batch job you must specify HELP, LIST, ALL, or at least one library name, because the batch job cannot prompt you for input.

You can specify up to eight parameters. If you specify more than one parameter, the parameters must be enclosed in parentheses and must be separated by commas.

Examples

• The following command outputs a list of all the libraries known to LIBDECOMP.COM:

  $ SUBMIT SYS$UPDATE:LIBDECOMP /PARAMETERS=LIST

• By default, the following command expands all eligible libraries:

  $ SUBMIT SYS$UPDATE:LIBDECOMP /PARAMETERS=ALL

• The following command expands the HELPLIB.HLB, STARLET.MLB, and LIB.MLB libraries:

  $ SUBMIT SYS$UPDATE:LIBDECOMP - _$ /PARAMETERS=(EXPAND,HELPLIB.HLB,STARLET.MLB,LIB.MLB)

An alternative to using the Library Decompression utility to expand or reduce an individual library is to use the DCL command LIBRARY with the /DATA qualifier. With this method, you can specify only one library per LIBRARY command.

Unlike LIBDECOMP.COM, which acts on only about 40 selected libraries that ship in data-reduced format, the LIBRARY command can be used to expand or reduce almost any library file, provided the library type (the file extension) is known to the OpenVMS Librarian utility. System libraries that you should not compress include the following:

• [SYSLIB]EPC$FACILITY.TLB
  This file ships empty.
• [SYSLIB]IMAGELIB.OLB
  Compression is not effective on this library.
• [SYSLIB]NCS$LIBRARY.NLB
  Library type .NLB is not known to the OpenVMS Librarian utility.

To expand a specified library, use the following command format:

LIBRARY library-name.ext /DATA=EXPAND

To reduce a specified library, use the following command format:

LIBRARY library-name.ext /DATA=REDUCE

You must always specify the library extension (.HLB, .MLB, .OLB, or .TLB).

If the specified library is not located on your current default device and directory, you must also specify the device and directory in the library specification. Most system libraries are in either SYS$HELP ([SYSHLP]) or SYS$LIBRARY ([SYSLIB]). For example:

$ LIBRARY [SYSHLP]HELPLIB.HLB /DATA=EXPAND

For information about other qualifiers for the LIBRARY command, see online help for LIBRARY or refer to the OpenVMS Command Definition, Librarian, and Message Utilities Manual.

17.10 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	Section 17.10.7
To improve system performance	Section 17.10.5
++On Alpha systems, to improve performance by using images with shared address data	Section 17.10.6
To make executable images that require enhanced privileges available for general use	Section 17.10.8.1
To allow a nonprivileged image to call the privileged functions of a shareable image	Section 17.10.8.2
To mark a sharable image as trusted so it can be invoked by privileged executable images	Section 17.10.9

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 Section 5.2.7.

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.

17.10.1 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 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 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 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.

17.10.2 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 Section 17.10.3).

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.

17.10.3 Understanding Attributes You Can Assign to Known Images

By specifying appropriate qualifiers to INSTALL commands, you can assign attributes to known images. Table 17-2 describes these attributes and the qualifiers that are used to assign them to known images.

Table 17-2 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
++ Resident	On Alpha 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

You can install images for the following reasons:

• Improve image activation performance
• On Alpha systems, improve execution performance of shared images
• Conserve physical memory
• Enhance privileges of images during excution

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.

17.10.5 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.

17.10.6 Installing Images with Shared Address Data

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

• At run time, shared address data saves physical memory because of increased memory sharing between processes.
• At image activation, shared address data reduces CPU and I/O time because fixup is performed at installation time.

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

Related Terms

Explanations of terms related to shared address data follow.

• Image section
  An image consists of a number of image sections. An image section can contain:
  • Instructions (code)
  • Read-only data (constants)
  • Read/write data
• Shared known images
  You can make an image a shared known image by using the following command:

  $ INSTALL ADD image-name /SHARED

  
  When you enter this command, the Install utility creates global sections for read-only image sections, allowing the sections to be shared by all the processes that run the image.

• Address data
  One kind of image section contains address data. At execution time, address data sections are read-only. However, the addresses are not known until image activation; therefore, the image section is read/write until the end of image activation. Addresses for a shareable image generally vary with the process because different processes are likely to have different collections of mapped images.
• Shared address data
  The shared address data feature assigns unique P1 space addresses for shareable images from the P1 image region. (The IMGREG_PAGES system parameter determines the size of the P1 space.) With the assigned address, the Install utility determines the content of an address data section when the image is installed. A global section is created to allow shared access to each address data image section.
  Executable (main) images can also use shared address data sections; these images are not assigned P1 addresses, however, because the base address for an executable image is determined when the image is linked.

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