Overview of Miscellaneous Parameters

The following miscellaneous configurable kernel parameters affect various, usually unrelated, HP-UX subsystems. For a concise list of miscellaneous parameters, see List of miscellaneous parameters.

Asynchronous Disk I/O Driver

The max_async_ports parameter governs the system-wide maximum number of ports to the asynchronous disk I/O driver that processes can have open at any given time.

System Clock

Two parameters, dst and timezone specify the style of Daylight Savings Time to be used, if any, and the relationship between the local time zone and Coordinated Universal Time (UCT), also sometimes called Greenwich Mean Time or GMT.

Fast Symbolic Link Traversal

create_fastlinks is a binary variable that tells the system to create symbolic links in a newer, more efficient format that reduces the number of disk-block accesses while performing pathname lookup operations.

Immediate Reporting on Disk I/O

default_disk_ir determines whether a write() returns immediately after the data is placed in the disk's write buffer or waits until the data is physically stored on the disk media.

o_sync_is_o_dsync determines whether an open()or fcntl() with the O_SYNC flag set can be converted to the same call with the O_DSYNC flag instead. This controls whether the function can return before updating the file-access time stamps after the file data is written to the disk.

Kernel-Panic Dumps

alwaysdump defines which classes of system memory are dumped to disk when a kernel panic occurs.

dontdump defines which classes of system memory are not dumped to disk when a kernel panic occurs.

initmodmax specifies the maximum number of kernel modules that are saved by a kernel-panic (system crash) dump operation.

Multi-Processor Spinlocks

These parameters control the allocation of spinlocks for use in systems equipped with multiple processors. They are intended for advanced users only and should not be altered without direct consultation with qualified HP field-support personnel. Setting any of these parameters to an inappropriate value can result in serious system-performance degradation:

bufcache_hash_locks: Buffer-cache spinlock pool
chanq_hash_locks: Channel queue spinlock pool
ftable_hash_locks: File-table spinlock pool
io_ports_hash_locks: I/O-port spinlock pool
pfdat_hash_locks: Pfdat spinlock pool
region_hash_locks: Process-region spinlock pool
sysv_hash_locks: System V Inter-process-communication spinlock pool
vnode_cd_hash_locks: Vnode clean/dirty spinlock pool
vnode_hash_locks: Vnode spinlock pool

See spinlock parameters for more information.

Distributed-Server Memory-Mapped I/O

clicreservedmem specifies how many bytes of system memory are to be reserved for I/O-mapping use by user processes in high-speed, distributed-server environments such as those used for running large database-processing programs.

Equivalently Mapped Memory

eqmemsize defines how much space is reserved for use as equivalently mapped memory, used primarily for handling DMA I/O transfers.

Maximum Users on System

maxusers is used by other system parameter definitions to allocate system resources based on the maximum number of users expected to be logged in on the system.

Queued Signals

Two parameters govern the behavior of queued signals. ksi_alloc_max sets the system-wide maximum number of queued signals that can be allocated, and ksi_send_max specifies the maximum number of queued signals that a process can send and have pending at one or more receivers at any given time.

Kernel Timeout-Scheduling Limit

ncallout limits the number of timeouts that can be scheduled by the kernel at any given time.

Telnet-Session Parameter

nstrtel defines how many telnet-session device files are available on the system.

Web-server Parameter

sendfile_max limits the amount of buffer cache that can be consumed and monopolized by the sendfile() system call on HP-UX web servers.

CD-ROM File-System Vnode-Table limit

ncdnode limits the number of entries in the vnode table for CD-ROM file systems, and thus the maximum number of CD-ROM file-system nodes that can be in memory at any given time.

Number of Blocks for tty and pty Transfers

nclist specifies how many cblocks are to be allocated for use in data transfers through tty and pty devices.

Device I/O Library Buffers

ndilbuffers limits the number of Device I/O Library devices that can be open at any given time.

Number of pty Entries

npty limits the number of pseudo-tty entries allowed on the system at any given time.

Enable Power-Fail Processing

pfail_enabled determines whether the power-fail routines are to be used or not upon loss of AC line power. Applies only on Series 800 systems that are equipped with power-fail hardware.

Enable Public Protection IDs on Shared Libs

public_shlibs enables (or disables) public protection IDs on shared libraries for improved system performance.

Real-Time Priority Levels

rtsched_numpri specifies how many distinct real-time interrupt priorities are available on the system.

ITE Console Scroll Size

scroll_lines defines the number of lines that can be scrolled on the internal terminal emulator (ITE) system console.

Reserved System Memory

unlockable_mem specifies how much system memory is to be reserved for system overhead and virtual memory management, and therefore cannot be locked by user processes.