HP 3000 Manuals HP 3000 Manuals
Appendix B Wait Reasons--Expanded Definitions
A process will be suspended if it cannot access a resource or it must
wait for another event to be completed. Although a process's wait reason
can pass through many different states between refresh intervals, HP
GlancePlus reports the state at the instant the process is displayed.
The following WAIT reasons occur for MPE/iX:
BREK IMP PAUS
CONS I/O RIN
CPU MEM SEM
DBMS MISC SIR
DISC MSG SON
FATH OTHR TERM
The specific WAIT REASONS can be defined as follows:
BREK The process is waiting to be resumed from a BREAK. For instance,
if a user who is running a program presses the Break key and
receives the colon (:) prompt, that process will show up in a
BREK wait.
CONS The process is waiting for a reply from the console operator. A
typical example would be a STORE with an outstanding tape
request at the console.
CPU The process is waiting to use the central processing unit. On
busy systems, higher priority processes can consume all of the
available CPU resources while lower priority processes must
wait. The PRI column displays the queue and priority number of
a process. On extremely busy systems, a low priority batch job
(high PRI number) can remain in a CPU wait state while all
available CPU resources are consumed by higher priority
processes (lower PRI number).
DBMS When SQL applications are running with multiple users, the
database monitor process (DBMON) will stay in the DBMS wait
state during periods of inactivity. This wait state is unique
to MPE/iX SQL applications.
When TurboIMAGE applications request a lock, the process will be
semaphore waited (SEM).
DISC The process is waiting for the completion of a read to a file or
write to a file. This does not include memory manager I/O,
which is accounted for in the MEM wait category. On MPE/iX
systems, main memory is used to buffer I/O requests; this
greatly reduces the amount of time a process waits on DISC.
FATH The son process is waiting for its father to reawaken it. When
one process creates a second process, the first process is
referred to as the father and the second process as the son.
The father process has the capability of starting and stopping
the son process.
IMP The process is impeded. This wait state is used for a variety
of reasons.
On MPE/iX systems, processes using databases make use of the
DBMS wait state.
I/O The process is waiting for the completion of nondisc I/O, such
as from magnetic tape. Disc I/O (DISC) and terminal I/O (TERM)
have separate wait states and are not included in this category.
MEM The process is waiting for library code, program code, data, or
any combination of the three to be brought into memory. Since
it would be wasteful for a large process to fully occupy main
memory, the process is broken up into smaller pieces, referred
to as pages. As these segments or pages of memory are needed,
they are brought into main memory from disc and the process must
memory (MEM) wait.
It is normal to find a process in this state occasionally.
Finding a single process in memory wait state repeatedly,
however, can be caused by poor locality--the process's logic is
forcing it to continually branch to other segments or pages.
Finding multiple processes in this state can indicate a lack of
main memory. As the demand for memory outstrips the supply, the
operating system must use a process's main memory for other,
higher priority processes.
MISC The process is waiting for an unspecified wait state and is
accumulated under this general category. HP GlancePlus reports
seldom-used wait states in this category.
MSG The process is waiting to receive a message. To synchronize
internal operations, some operating system processes communicate
by sending internal messages to one another. MPE message file
waits, RECEIVEMAIL intrinsic waits, and interprocess
communication (IPC) waits are examples of user-generated message
wait state.
OTHR The process is waiting for an unspecified wait state called
OTHR, which excludes all of the other wait states. OTHR appears
as an (O) in the wait reasons and the wait-state bar in the
Process display.
PAUS The application program calls the PAUSE intrinsic, which delays
the program for a user-specified length of time. The program is
currently waiting for this time to elapse before continuing.
RIN Specific resources can be shared by a set of processes. MPE
provides users with a RIN (resource identification number)
facility to prevent two processes from using a shared resource
at the same time. When one process locks a specific RIN, a
second process wanting to lock the same RIN will wait. A RIN
wait applies to both global and local RINs. RINs are also used
to lock MPE/iX files.
SEM The process is waiting for a software semaphore or flag other
than those specified by SIR and RIN wait categories.
SIR To maintain consistency, certain operating system functions are
performed serially by a single process. To enforce this access
pattern, a software resource called a SIR is obtained before the
critical function is performed. SIRs are internally-used MPE
resources and are not available to users directly.
SON The father process is waiting to be reawakened by its son
process. When one process creates a second process, the first
process is referred to as the father and the second as the son.
The father process has the capability of starting the son and
continuing to process, or starting the son and waiting until it
is reawakened by the son.
TERM The process is waiting for the completion of a terminal read.