IBM AIX Continuous Availability Features - IBM Redbooks

Note: Executing errctrl with the –P flag will apply the changes for future reboots as well.
There was no support for the -P flag in prior AIX versions.
To display the current RTEC level for xmalloc and its subcomponents, execute the following
command:
errctrl -c alloc -q -r
Example 3-44 RTEC level for alloc and its subcomponent
# errctrl -c alloc -q -r
---------------------------------------------+-------+-------+-------+--------
| Have |ErrChk |LowSev |MedSev
Component name | alias | /level| Disp | Disp
---------------------------------------------+-------+-------+-------+-------alloc
.heap0 | NO | ON /0 | 48 | 64
.xmdbg | NO | ON /9 | 64 | 80
Example 3-44 shows the RTEC level for alloc and its subcomponents. Note that alloc.xmdbg
is set to errorcheckmaximum (which is explained in more detail in 3.9.3, “Run-time error
checking (RTEC) levels for XMDBG (alloc.xmdbg)” on page 127). In this example,
alloc.heap0 has no error checking enabled.
To display the current RTEC level for any subcomponent of xmalloc, execute:
errctrl -c alloc. -q -r
For example, the command errctrl -c alloc.xmdbg -q -r will show the RTEC level for
alloc.xmdbg.
3.9.3 Run-time error checking (RTEC) levels for XMDBG (alloc.xmdbg)
The probability of taking each option will be determined by the debug level set for the
alloc.xmalloc component. However, there is also a way to tune individual probabilities to
desired levels. For further information about forcing individual tunables, refer to 3.9.4,
“XMDBG tunables affected by error check level” on page 131.
Error checking characteristics can be changed for xmalloc subsystem with
component-specific tunables. All options can be configured at run time by using the errctrl
command.
Minimal Error Checking Level
When the error-checking level is set to minimal (level 1), the checks and techniques used by
xmalloc are applied at fairly low frequencies. It can be set to minimal by executing:
errctrl -c alloc.xmdbg errcheckminimal
The frequency of various xmalloc debug tunables can be viewed by using the kdb
subcommand xm –Q. Example 3-45 on page 128 shows the frequencies for various tunables.
Minimal checking is the default checking level on version 5. The frequency that appears next
to each tunable is proportional to the frequency base (1024). From the example, you can see
that the Ruin All Data technique will be applied 5 times out of every 1024 (0x400) calls to
xmalloc() (about 0.5% of every 1024 xmalloc() calls). Also, 16 byte allocations will be
promoted about 10 times out of every 1024 calls to xmalloc(), which is about 1% of the time.
Chapter 3. AIX advanced continuous availability tools and features 127