HP OpenVMS Systems Documentation
OpenVMS System Manager's Manual
15.10 Tuning BAP System Parameters
OpenVMS Alpha Version 7.1 and later contains system parameters that control the operation of bus-addressable pool (BAP). AUTOGEN sets these parameters correctly. If you choose to skip AUTOGEN, follow the instructions in this section to set the BAP parameters.
The CIPCA, CIXCD, KFMSB, and Qlogic 1020ISP adapters are the first among an expanding list of adapters to use bus-addressable pool (BAP). BAP is a non-paged dynamic, physical-address-filtered memory pool used to overcome I/O bus and 32-bit adapter physical addressing limits.
The following list contains the system parameters that control the operation of BAP:
If one or more system adapters use BAP, you must adjust the BAP system parameters after installing or upgrading the operating system: You can do this automatically using AUTOGEN with the FEEDBACK qualifier. The typical AUTOGEN with FEEDBACK command to set these parameters follows:
If you prefer not to use this command because you want to adjust only the BAP parameters settings, you can use the following procedure:
The BAP allocation amount depends on the adapter type, the number of adapters, and the version of the operating system. The size of physical memory and the I/O bus determine whether the BAP remains separate or is merged with normal nonpaged dynamic memory (NPAGEDYN).
The general rule that determines whether BAP remains separate follows:
For systems whose BAP is merged with nonpaged pool, the initial amount and maximum amount of nonpaged pool (as displayed by the DCL command SHOW MEMORY/POOL/FULL) do not match the value of the NPAGEDYN and NPAGEVIR system parameters. Instead, the value of the NPAG_BAP_MIN system parameter is added to NPAGEDYN to determine the initial size, and the value of NPAG_BAP_MAX is added to NPAGEVIR to determine the maximum size.
On OpenVMS systems with merged BAP, the values of the NPAGEDYN... system parameters typically need to be increased. After your system has been running a few days, you can adjust these values by one of the following three methods:
|Displaying information about page and swap files||Section 16.3|
|Calculating appropriate sizes for files||Section 16.4|
|Minimizing dump file size when disk space is insufficient||Section 16.5|
|Writing a dump file on a system disk with multiple paths or shadow set members||Section 16.6|
|Writing the dump file to a device other than the system disk||Section 16.7|
|Using SDA to analyze the contents of a crash dump||Section 16.8|
|++Using SDA CLUE commands to obtain and analyze summary crash dump information||Section 16.9|
|+Using CLUE to obtain historical information about crash dumps||Section 16.10|
|Saving the contents of the system dump file after a system failure||Section 16.11|
|Copying dump files to tape or disk||Section 16.12|
|Freeing dump information from the page file||Section 16.13|
|Installing page and swap files||Section 16.14|
|Removing page, swap, and dump files||Section 16.15|
|Creating and modifying page, swap, and dump files||Section 16.16|
|Controlling access to process dumps||Section 16.17.2|
This chapter explains the following concepts:
|Understanding dump files||Section 16.1|
|Understanding page and swap files||Section 16.2|
|Understanding the order of information in a selective system dump||Section 16.5.1|
|++Understanding SDA CLUE||Section 16.9.1|
|+Understanding CLUE||Section 16.10.1|
|Understanding process dumps||Section 16.17|
When the operating system detects an unrecoverable error or an inconsistency within itself that causes the system to fail, it writes the contents of the error log buffers, processor registers, and memory into the system dump file, overwriting its previous contents.
The contents of error log buffers are also written to the error log dump file. The error log dump file is provided so that the system can be updated on reboot to include error log entries that were created but not written at the time of a system crash.
Be sure to wait until you see the termination message before using the console terminal to halt the system. If you do not wait, your system might not save a complete system dump file.
The default system dump file, SYS$SPECIFIC:[SYSEXE]SYSDUMP.DMP, is created during installation. (You do not need a system dump file to run the operating system. However, you must have a system dump file to diagnose system crashes.) AUTOGEN automatically determines an appropriate size for the system dump file for your hardware configuration and system parameters. Refer to Section 16.5 for information about minimizing system dump file size if disk space is insufficient.
For special configurations or varying work loads, you can change the size of the system dump file. For information, see Section 16.16.1. You can write the system dump file on a disk other than the system disk. This is referred to as dump off system disk (DOSD). For more information, see Section 16.7.
AUTOGEN creates the error log dump file during installation; its size depends on your configuration and system parameters. Error log dump files on VAX and Alpha systems have the following differences:
The operating system uses the latest version of SYS$SYSTEM:SYSDUMP.DMP to store system crash dumps. If SYSDUMP.DMP does not exist in SYS$SYSTEM, the operating system uses the system page file, SYS$SYSTEM:PAGEFILE.SYS, overwriting the contents of that file.
If the SAVEDUMP system parameter is set, the crash dump is retained in PAGEFILE.SYS when the system is booted. If SAVEDUMP is clear, the system uses the page file for paging; any dump written to the page file is lost.
If you use SYS$SYSTEM:PAGEFILE.SYS to capture system crash dumps, you should later free the space occupied by the dump for use in system paging, with either of the following methods:
For detailed instructions, see Section 16.13.
Include the appropriate commands in the SYSTARTUP_VMS.COM startup command procedure to free dump information from the page file each time the system reboots.
Be careful when using the page file for selective dumps. Selective dumps use up all available space. If your page file is small, selective dump information might fill the entire page file, leaving no space for paging during system boot. This can cause the system to hang during reboot.
The two types of system dumps are physical and selective. Table 16-1 defines physical and selective system dumps. Table 16-3 compares the information available in physical and selective system dump files.
|Physical dump||Writes the entire contents of physical memory to the system dump file. To ensure a useful physical dump, the system dump file must be large enough to contain all of physical memory.|
|Selective dump||Stores those portions of memory most likely to be useful in crash dump analysis. A selective system dump is useful when disk space is not available to hold all of physical memory.|
A system dump file has the NOBACKUP attribute; therefore, the Backup utility (BACKUP) does not copy the file unless you use the qualifier /IGNORE=NOBACKUP when invoking BACKUP. When you use the SDA COPY command to copy the system dump file to another file, the operating system does not automatically set the new file to NOBACKUP. If you want to set the NOBACKUP attribute on the copy, use the SET FILE command with the /NOBACKUP qualifier as described in the OpenVMS DCL Dictionary.
By default, SYS$SYSTEM:SYSDUMP.DMP is protected against world access.
Because a system dump file can contain privileged information, you
should keep this level of protection on system dump files. Similarly,
when you copy system dump files using the System Dump Analyzer utility
(SDA) as explained in Section 16.11 and Section 16.13, be sure to
protect the copy from world read access. For more information about
file protection, refer to the OpenVMS Guide to System Security.
16.2 Understanding Page and Swap Files
As part of memory management, the operating system makes efficient use of physical memory by moving information between physical memory and files stored on disk. The system does this in two ways: paging and swapping. Table 16-2 defines these and related terms.
|Paging||A memory management operation that provides the efficient use of physical memory allotted to a process. Paging moves infrequently used portions of a process workspace out of physical memory to a file. For more information about paging, refer to the OpenVMS Performance Management manual.|
|Page file||The file to which the system writes paged portions of memory. The OpenVMS installation process creates a page file named SYS$SYSTEM:PAGEFILE.SYS. If necessary, you can use SYS$SYSTEM:PAGEFILE.SYS in place of the system crash dump file. For more information, see Section 16.1.1.|
|Swapping||A memory management operation that provides the efficient use of physical memory available for the entire system. Swapping moves the entire workspace of a less active process out of physical memory to a file. For more information about swapping, refer to the OpenVMS Performance Management manual.|
|Swap file||The file to which the system writes swapped portions of memory. The OpenVMS installation procedure creates a swap file named SYS$SYSTEM:SWAPFILE.SYS.|
|Primary page and swap files||The default page and swap files created during OpenVMS installation. These files are named SYS$SYSTEM:PAGEFILE.SYS and SYS$SYSTEM:SWAPFILE.SYS.|
|Secondary page and swap files||Additional page and swap files that you might create for performance or disk space reasons. If you kept the primary page and swap file on the system disk, the system uses the space in the secondary files for paging and swapping in addition to the space in the primary page and swap files. For information about creating secondary page and swap files, see Section 16.16.|
Page and swap files must be installed before the system can use them. The system automatically installs the latest versions of SYS$SYSTEM:PAGEFILE.SYS and SWAPFILE.SYS during startup. If you create secondary page and swap files, you must make sure the system installs them during startup. For more information about installing page and swap files, see Section 16.14.
AUTOGEN automatically determines appropriate sizes for the files for your hardware configuration and system parameters. For special configurations or varying work loads, you might want to change the size of the page or swap file. For information, see Section 16.16.1.
If your system does not require the page file for storing system crash dumps, you can move it off the system disk. However, you should keep one page file on the system disk, if possible, so that you can boot the system if another disk holding the page files becomes unavailable. The swap file can also be moved off the system disk.