Database Reference
In-Depth Information
for user tasks. During periods of heavy activity, if there is a shortage or high demand for resources, which process gets
the available resource—such as CPU cycles—depends on where in the run queue the process is currently located,
and this depends on the priority of the process. This means that scheduling delays and run queue lengths of the
operating system affects the execution of tasks.
[oracle@ssky1l4p1 ~]$ ps -flcae | egrep "TTY|ora_d"
F S UID PID PPID CLS PRI ADDR SZ WCHAN STIME TTY TIME CMD
0 S oracle 6206 1 TS 19 - 382802 poll_s 01:53 ? 00:00:59 ora_diag_SSKYDB_2
0 S oracle 6212 1 TS 19 - 382177 semtim 01:53 ? 00:00:04 ora_dbrm_SSKYDB_2
0 S oracle 6224 1 TS 19 - 385078 poll_s 01:53 ? 00:02:56 ora_dia0_SSKYDB_2
0 S oracle 7616 1 TS 19 - 384140 semtim 01:57 ? 00:00:12 ora_dbw0_SSKYDB_2
0 S oracle 7671 1 TS 19 - 381931 epoll_ 01:57 ? 00:00:00 ora_d000_SSKYDB_2
Here is the description of the various columns:
UID
—The user that created the O/S process. In this case,
Oracle
user on the database cluster
created the process.
•
PID
—Process ID. The PID is assigned by the O/S when the process is added to the run queue.
•
PPID
—Parent process ID. This Indicates these processes are children to those listed in the PID.
•
CLS
—Class of the process. The class is assigned to the process when the process starts
execution by the application that starts it. In this case, Oracle assigns at what class the
process should run.
TS
(“Time Sharing”) is the default class. The other types of classes are
RT
(“Real Time”),
RR
(“Round Robin”), and
FF
(FIFO).
•
PRI
—Priority of the process. PRI indicates at what priority the process is currently executing.
The priority also determines where in the run queue the process is placed and how soon and
how much CPU the scheduler will assign the process.
•
CMD
—The actual command being executed by the process.
•
Classes
Depending on the O/S, UNIX or Linux, or the flavor of UNIX, there are several types of classes:
•
Time sharing (
TS
)
Fixed priority (
•
FX
)
•
System (
SYS
)
Real Time (
•
RT
)
Round Robin (
•
RR
)
First in First Out (
•
FF
)
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