Virtual X$ tables¶
Some X$ tables are not coming from the kqftab structure.
Let us find out their origin.
It can be seen that the xinfo tool outputs only 1,272 tables in 21.5, whereas X$KQFTA has 1,377 rows:
[oracle@db-21 sf_exchange]$ xinfo list -o json |
> jq -r '.[] | .nam' |
> awk '{printf "%4d %s\n",NR,$0}'
1 X$KQFTA
2 X$KQFVI
3 X$KQFVT
4 X$KQFDT
5 X$KQFCO
..
1271 X$BCAPPLY_STATS
1272 X$FSDDBFS
What about extra 105 rows?
Let me show what the output of X$KQFTA is like in my database:
SQL> select * from x$kqfta;
ADDR INDX INST_ID CON_ID KQFTAOBJ KQFTAVER KQFTANAM KQFTATYP KQFTAFLG KQFTARSZ KQFTACOC
---------------- ---------- ---------- ---------- ---------- ---------- ------------------------------ ---------- ---------- ---------- ----------
0000000016CDBF20 0 1 0 4294950912 6 X$KQFTA 4 0 80 11
0000000016CDBF70 1 1 0 4294950913 3 X$KQFVI 1 0 80 7
..
0000000016CF4C00 1270 1 0 4294956360 2 X$BCAPPLY_STATS 4 2 260 16
0000000016CF4C50 1271 1 0 4294956225 2 X$FSDDBFS 4 0 1144 14
000000008F8127C0 1272 1 0 4294953644 0 X$KSIPC_PROC_STATS 9 18 0 0
000000008F812810 1273 1 0 4294953645 0 X$KSIPC_INFO 9 18 0 0
000000008F812860 1274 1 0 4294952215 1 X$KSXPTESTTBL 10 2 146 15
000000008F8128B0 1275 1 0 4294952216 0 X$KSXP_STATS 9 18 0 0
000000008F812900 1276 1 0 4294952217 0 X$SKGXP_PORT 9 18 0 0
000000008F812950 1277 1 0 4294952218 0 X$SKGXP_CONNECTION 9 18 0 0
000000008F8129A0 1278 1 0 4294952219 0 X$SKGXP_MISC 9 18 0 0
000000008F8129F0 1279 1 0 4294952227 1 X$KTCNQROW 9 2 1480 47
..
000000008F8147F0 1375 1 0 4294954950 3 X$DIAG_VTEST_EXISTS 10 34 1536 13
000000008F814840 1376 1 0 4294954964 3 X$DIAG_VADR_CONTROL 10 34 1072 21
1377 rows selected.
It can be seen that starting at INDX=1,272 (which is row 1,273 because INDX starts at 0) the ADDR value is quite different - it is 0x8F8127C0.
It is not an address from the Oracle binary anymore:
SQL> select *
2 from x$ksmsp
3 where to_number('8F8127C0','XXXXXXXXXXXXXXXX')
4 between to_number(ksmchptr,'XXXXXXXXXXXXXXXX')
5 and to_number(ksmchptr,'XXXXXXXXXXXXXXXX') + ksmchsiz - 1;
ADDR INDX INST_ID CON_ID KSMCHIDX KSMCHDUR KSMCHCOM KSMCHPTR KSMCHSIZ KSMCHCLS KSMCHTYP KSMCHPAR
---------------- ---------- ---------- ---------- ---------- ---------- ---------------- ---------------- ---------- -------- ---------- ----------------
00007F6C5E50DC10 106576 1 1 1 1 KQF runtime def 000000008F8127B0 8416 perm 0 000000008F101000
The address refers to the KQF runtime def area of SGA.
The X$ tables starting from INDX=1,272 are what Oracle is called virtual tables in its code.
Of course, the INDX value is version dependent but these virtual tables always come after other X$ tables defined in kqftab.
The starting address of the virtual tables can be obtained from the kqftvrt_ SGA variable:
SQL> oradebug dumpvar sga kqftvrt_
struct kqftv* kqftvrt_ [0600A7408, 0600A7410) = 8F8127C0 00000000
The virtual tables are built inside the kqfbldtvrt function.