hp-ux 11.23 error reducing dbc_max_pct

[cristian_5]

hi all.
on a HP-UX 11.23 system i was trying to reduce the dbc_max_pct value but i encountered this error:

kctune dbc_max_pct=10
* The automatic 'backup' configuration has been updated.
ERROR: Failed to grow the buffer cache to the proposed new lower
limit.

may anyone help me?
thanks.

cristian

[James R. Ferguson]

Hi Cristian:

What is your value of 'dbc_min_pct'?. The value for 'dbc_max_pct' must be equal or greater than that for 'dbc_min_pct'.

Regards!

...JRF...

[cristian_5]

kctune dbc_max_pct dbc_min_pct
Tunable Value Expression Changes
dbc_max_pct 50 Default Immed
dbc_min_pct 5 Default Immed


consider that on another system (totally equivalent to this one) i reduced the value without problem.
may be a problem of buffer cache occupation?

also using "sync" for flushing BC before issuing the command does not work.

[cristian_5]

i've just tried again and this time the command succeded:

kctune dbc_max_pct=10
* The automatic 'backup' configuration has been updated.
* The requested changes have been applied to the currently
running system.
Tunable Value Expression Changes
dbc_max_pct (before) 50 50 Immed
(now) 10 10

kctune dbc_max_pct dbc_min_pct
Tunable Value Expression Changes
dbc_max_pct 10 10 Immed
dbc_min_pct 5 Default Immed


perhaps the system was not so stressed ...

[James R. Ferguson]

Hi (again) Cristian:

My guess would be that the first allotted time for 'syncer' to flush modified buffers was insufficient to achieve the degree of reduction you specified. As I recall there were changes made in 11.23 to improve buffer cache management and reduce the overhead that could occur during its activity.

Regards!

...JRF...

[cristian_5]

JRF, thanks for attention.
regards.

cristian

[cristian_5]

thread closed.