Virtual X$ tables

Some of X$ tables are not coming from the kqftab structure. For example, 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.