This parameter specifies the interval (in seconds) at which Oracle collects operating statistics. Statistics are only collected when a request is made from the client to the server, or when a request completes.

Version Type Default Session
8.0.4 Integer 0 Yes Immediate
8.0.5 Integer 0 Yes Immediate
8.0.6 Integer 0 Yes Immediate
8.1.5 Integer 0 Yes Immediate
8.1.6 Integer 0 Yes Immediate
8.1.7 Integer 0 Yes Immediate
9.0.1 Integer 0 Yes Immediate
9.2.0 Integer 0 Yes Immediate

When TIMED_OS_STATISTICS is enabled statistics are collected as follows:

The default value of zero specifies that operating system statistics are not gathered.

On older systems gathering operating system statistics was very expensive and Oracle recommended:

The parameter can be set in the initialisation file e.g.

timed_os_statistics = 30

This parameter can be set at system level e.g.

    ALTER SYSTEM SET timed_os_statistics = 30

This parameter can be set at session level e.g.

    ALTER SESSION SET timed_os_statistics = 0

This parameter is apparently not supported on Windows NT or Windows 2000.

Operating system (OS) statistics belong to statistics class 16 (see V$STATNAME.CLASS)

In Oracle 8.0.4 and above the value of TIMED_OS_STATISTICS is the number of seconds

In Oracle 7.3.4 and below, TIMED_OS_STATISTICS can take one of the following values

Value Description
OFF Do not gather operating system statistics. This is the default value
CALL Gather statistics at every push or pop call. This option has significant overhead
LOGOFF Gather statistics when the user logs off from an Oracle session

Statistics affected by enabling TIMED_OS_STATISTICS include:

OS User level CPU time
OS System call CPU time
OS Other system trap CPU time
OS Text page fault sleep time
OS Data page fault sleep time
OS Kernel page fault sleep time
OS User lock wait sleep time
OS All other sleep time
OS Wait-cpu (latency) time
OS Minor page faults
OS Major page faults
OS Swaps
OS Input blocks
OS Output blocks
OS Messages sent
OS Messages received
OS Signals received
OS Voluntary context switches
OS Involuntary context switches
OS System calls
OS Chars read and written
OS Process heap size
OS Process stack size

The statistics collected may vary by platform and release. The above table represents statistics collected for Oracle 9.2 on Solaris