Monitoring Physical logging
Question: does the physical log use extents, and why does onstat -d show 0 pages free for the physical-log dbspace while onstat -l shows almost nothing used? Answers: the physical log has no extents — its space is allocated as one contiguous chunk, so it always appears fully used in onstat -d; it works as a circular buffer. Current usage is read from onstat -l's physical logging section (physize, phyused, %used) — onstat -F only shows page cleaners. The same data is available in sysmaster via 'select pl_physize, pl_phyused from sysplog' (free pages = pl_physize - pl_phyused). Resolved.
Auto-generated by DrWatson from the posts below — may be imperfect; read the full thread.
Informix Version 10:
Does physical log have extents ? It may sound a dumb question, but
what I am seeing is that in onstat -d physical log show 0 pages free
but I don't see any errors. onstat -l report .05% used. So I am
wondering, is it like other dbspaces where once the space is allocated
for extent it doesn't show up as free even though it has free space
inside the extent. I tried to do a lookup in sysptnhdr for physical
log dbspace as we have separate dbspace for physical log but couldn't
find any record, may be I am assuming things incorrectly.
On Dec 10, 4:28 pm, mohitanch...@gmail.com wrote:
> Informix Version 10:
>
> Does physical log have extents ? It may sound a dumb question, but
> what I am seeing is that in onstat -d physical log show 0 pages free
> but I don't see any errors. onstat -l report .05% used. So I am
> wondering, is it like other dbspaces where once the space is allocated
> for extent it doesn't show up as free even though it has free space
> inside the extent. I tried to do a lookup in sysptnhdr for physical
> log dbspace as we have separate dbspace for physical log but couldn't
> find any record, may be I am assuming things incorrectly.
No the physical log has no extents. Once the space is allocated to it
from a chunk, the space would show as used in onstat -d output, but to
see how much space is available in your physical log at anytime you'd
want to look at the onstat -l information in the physical logging
section. The physical log is used like a big circular buffer, filled
from start to end, then once at the end, it wraps back around to the
start (assuming it's not going to over write anything required to
complete physical recovery).
On Dec 10, 5:28 pm, mohitanch...@gmail.com wrote:
> Informix Version 10:
>
> Does physical log have extents ? It may sound a dumb question, but
> what I am seeing is that in onstat -d physical log show 0 pages free
> but I don't see any errors. onstat -l report .05% used. So I am
> wondering, is it like other dbspaces where once the space is allocated
> for extent it doesn't show up as free even though it has free space
> inside the extent. I tried to do a lookup in sysptnhdr for physical
> log dbspace as we have separate dbspace for physical log but couldn't
> find any record, may be I am assuming things incorrectly.
You monitor how much of the physical log is being used at any given
moment with onstat -F.
Space allocated to the physical log is treated as a single contiguous
extent.
On Dec 10, 3:05 pm, "Art S. Kagel" <art.ka...@gmail.com> wrote:
> On Dec 10, 5:28 pm, mohitanch...@gmail.com wrote:
>
> >InformixVersion 10:
>
> > Does physical log have extents ? It may sound a dumb question, but
> > what I am seeing is that in onstat -d physical log show 0 pages free
> > but I don't see any errors. onstat -l report .05% used. So I am
> > wondering, is it like other dbspaces where once the space is allocated
> > for extent it doesn't show up as free even though it has free space
> > inside the extent. I tried to do a lookup in sysptnhdr for physical
> > log dbspace as we have separate dbspace for physical log but couldn't
> > find any record, may be I am assuming things incorrectly.
>
> You monitor how much of the physical log is being used at any given
> moment with onstat -F.
>
> Space allocated to the physical log is treated as a single contiguous
> extent.
onstat -F just gives the status of page cleaners. Is there some fieldI need to look at ?
However, onstat -l gives following output, which field should I look
at to see the available space at a given point
Physical Logging
Buffer bufused bufsize numpages numwrits pages/io
P-2 0 96 7378 2454 3.01
phybegin physize phypos phyused %used
2:53 200000 960 2 0.00
Also, can I use sysmaster database to get that information
On Dec 11, 11:33 am, mohitanch...@gmail.com wrote:
> On Dec 10, 3:05 pm, "Art S. Kagel" <art.ka...@gmail.com> wrote:
>
>
>
> > On Dec 10, 5:28 pm, mohitanch...@gmail.com wrote:
>
> > >InformixVersion 10:
>
> > > Does physical log have extents ? It may sound a dumb question, but
> > > what I am seeing is that in onstat -d physical log show 0 pages free
> > > but I don't see any errors. onstat -l report .05% used. So I am
> > > wondering, is it like other dbspaces where once the space is allocated
> > > for extent it doesn't show up as free even though it has free space
> > > inside the extent. I tried to do a lookup in sysptnhdr for physical
> > > log dbspace as we have separate dbspace for physical log but couldn't
> > > find any record, may be I am assuming things incorrectly.
>
> > You monitor how much of the physical log is being used at any given
> > moment with onstat -F.
>
> > Space allocated to the physical log is treated as a single contiguous
> > extent.
>
> onstat -F just gives the status of page cleaners. Is there some field> I need to look at ?
>
> However, onstat -l gives following output, which field should I look
> at to see the available space at a given point
>
> Physical Logging
> Buffer bufused bufsize numpages numwrits pages/io
> P-2 0 96 7378 2454 3.01
> phybegin physize phypos phyused %used
> 2:53 200000 960 2 0.00
>
> Also, can I use sysmaster database to get that information
You'd look at phyused which is in pages so in this output you are
using 2 out of 200000 pages (physize is also expressed in pages) or
you have 199998 free pages in the physical log, or you can use the
%used field.
On Dec 11, 9:03 am, jpren...@yahoo.com wrote:
> On Dec 11, 11:33 am, mohitanch...@gmail.com wrote:
>
>
>
>
>
> > On Dec 10, 3:05 pm, "Art S. Kagel" <art.ka...@gmail.com> wrote:
>
> > > On Dec 10, 5:28 pm, mohitanch...@gmail.com wrote:
>
> > > >InformixVersion 10:
>
> > > > Does physical log have extents ? It may sound a dumb question, but
> > > > what I am seeing is that in onstat -d physical log show 0 pages free
> > > > but I don't see any errors. onstat -l report .05% used. So I am
> > > > wondering, is it like other dbspaces where once the space is allocated
> > > > for extent it doesn't show up as free even though it has free space
> > > > inside the extent. I tried to do a lookup in sysptnhdr for physical
> > > > logdbspaceas we have separatedbspacefor physical log but couldn't
> > > > find any record, may be I am assuming things incorrectly.
>
> > > You monitor how much of the physical log is being used at any given
> > > moment with onstat -F.
>
> > > Space allocated to the physical log is treated as a single contiguous
> > > extent.
>
> > onstat -F just gives the status of page cleaners. Is there some field> > I need to look at ?
>
> > However, onstat -l gives following output, which field should I look
> > at to see the available space at a given point
>
> > Physical Logging
> > Buffer bufused bufsize numpages numwrits pages/io
> > P-2 0 96 7378 2454 3.01
> > phybegin physize phypos phyused %used
> > 2:53 200000 960 2 0.00
>
> > Also, can I use sysmaster database to get that information
>
> You'd look at phyused which is in pages so in this output you are
> using 2 out of 200000 pages (physize is also expressed in pages) or
> you have 199998 free pages in the physical log, or you can use the
> %used field.- Hide quoted text -
>
> - Show quoted text -
Is it possible to get this information from sysmaster database
On Dec 11, 3:57 pm, mohitanch...@gmail.com wrote:
> On Dec 11, 9:03 am, jpren...@yahoo.com wrote:
>
>
>
> > On Dec 11, 11:33 am, mohitanch...@gmail.com wrote:
>
> > > On Dec 10, 3:05 pm, "Art S. Kagel" <art.ka...@gmail.com> wrote:
>
> > > > On Dec 10, 5:28 pm, mohitanch...@gmail.com wrote:
>
> > > > >InformixVersion 10:
>
> > > > > Does physical log have extents ? It may sound a dumb question, but
> > > > > what I am seeing is that in onstat -d physical log show 0 pages free
> > > > > but I don't see any errors. onstat -l report .05% used. So I am
> > > > > wondering, is it like other dbspaces where once the space is allocated
> > > > > for extent it doesn't show up as free even though it has free space
> > > > > inside the extent. I tried to do a lookup in sysptnhdr for physical
> > > > > logdbspaceas we have separatedbspacefor physical log but couldn't
> > > > > find any record, may be I am assuming things incorrectly.
>
> > > > You monitor how much of the physical log is being used at any given
> > > > moment with onstat -F.
>
> > > > Space allocated to the physical log is treated as a single contiguous
> > > > extent.
>
> > > onstat -F just gives the status of page cleaners. Is there some field> > > I need to look at ?
>
> > > However, onstat -l gives following output, which field should I look
> > > at to see the available space at a given point
>
> > > Physical Logging
> > > Buffer bufused bufsize numpages numwrits pages/io
> > > P-2 0 96 7378 2454 3.01
> > > phybegin physize phypos phyused %used
> > > 2:53 200000 960 2 0.00
>
> > > Also, can I use sysmaster database to get that information
>
> > You'd look at phyused which is in pages so in this output you are
> > using 2 out of 200000 pages (physize is also expressed in pages) or
> > you have 199998 free pages in the physical log, or you can use the
> > %used field.- Hide quoted text -
>
> > - Show quoted text -
>
> Is it possible to get this information from sysmaster database
Ah, found it.
You could run select pl_physize, pl_phyused from sysplog.
If you wanted it in terms of free pages you could do something like
select (pl_physize - pl_phyused) free_pages from sysplog
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