Re: Direct SGA access problem because of structs' changing start address
- From: "keydana@xxxxxx" <keydana@xxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Wed, 8 Jan 2014 23:06:51 +0100
Hi Jonathan, & hi Frits & all,
thanks a lot, but could you please elaborate? In fact when I query
select min(KSMCHPTR), max(KSMCHPTR), min(addr), max(addr) from x$ksmsp;
from different sessions and in different instances, really the min(KSMCHPTR)
and max(KSMCHPTR) seem to be constant... Does this mean the ADDR reflects
private process memory locations, and the KSMCHPTR, the shared memory addresses
I want to read from?
Extending the query I was using to get the row size,
select addr,
to_number(rawtohex(addr), 'XXXXXXXXXXXXXXXX') decaddr,
abs(to_number(rawtohex(addr), 'XXXXXXXXXXXXXXXX') -
to_number(rawtohex(lag(addr) over (order by addr)), 'XXXXXXXXXXXXXXXX'))
itemsize,
ksmchptr,
to_number(rawtohex(KSMCHPTR), 'XXXXXXXXXXXXXXXX') decptr,
abs(to_number(rawtohex(KSMCHPTR), 'XXXXXXXXXXXXXXXX') -
to_number(rawtohex(lag(KSMCHPTR) over (order by KSMCHPTR)),
'XXXXXXXXXXXXXXXX')) ptrsize
from x$ksmsp
order by KSMCHPTR
fetch next 10 rows only;
ADDR DECADDR ITEMSIZE KSMCHPTR
DECPTR PTRSIZE
---------------- ------------------------ ---------- ----------------
---------- ----------
00007F182EC44308 139741840556808 88 0000000062000058 1644167256
00007F182EC44360 139741840556896 88 00000000620000B0
1644167344 88
00007F182EC443B8 139741840556984 88 00000000620000E0
1644167392 48
00007F182EC44410 139741840557072 88 00000000620CCFD0
1645006800 839408
00007F182EC44468 139741840557160 88 00000000620CD000
1645006848 48
00007F182EC444C0 139741840557248 88 0000000062A95A88
1655265928 10259080
00007F182EC44518 139741840557336 88 0000000062A96A88
1655270024 4096
00007F182EC44570 139741840557424 88 0000000062A97A88
1655274120 4096
00007F182EC445C8 139741840557512 88 0000000062A98A88
1655278216 4096
00007F182EC44620 139741840557600 88 0000000062A99A88
1655282312 4096
... on the other hand, I think I misunderstood, this looks more like the lag in
ksmchptr reflects the actual chunk size, so this won't probably be what I need
to read...
Sorry I'm confused, but it's the first time I'm looking into this... As for
x$ksmfsv, this looks like variable locations and their types, but how could I
make use of that?
It would be great if you could take the time to explain a little further. To be
honest I don't understand, either,
"find the linked list that connects all the items in the shared pool"
... I thought that while LRU list and free list(s) are linked lists running
through the shared pool, with x$ksmsp I'd just be reading, kind of,
sequentially from memory, like in a dump - or does it represent yet another
linked list?
Thanks a lot, again,
Sigrid
>> x$ksmsp looks like a segmented array dynamically created in your session
>> memory. (Check the addr value against the min() and max() ksmchptr.)
>> You need some other way to find the linked list that connects all the items
>> in
>> the shared pool - which probably means checking the right variables in
>> x$ksmfsv
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