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Informix - Problem description

Problem IT29322 Status: Closed

WHEN RTREE NODE SPLITS AND HDR/RSS CONFIGURED, PAGES ON HDR/RSS GET OUT OF
SYNC WITH PRIMARY DUE TO SLOT LENGTH DIFFERENCE

product:
INFORMIX SERVER / 5725A3900 / B70 - IDS 11.70
Problem description:
So if you create a table that has a spatial column and then
create an rtree index on that column.  When you do this and rows
are inserts until an index node has to split then on 1 of the 2
pages involved in the split, there will be 1 slot that is larger
on the primary server than on the hdr/rss node.

Example oncheck -pp output showing difference.

From the primary:
oncheck -pp 3145732 13
addr             stamp    chksum nslots flag type         frptr
frcnt next     p
rev
3:140            607767   4691   33     881  DATA         2690
1270  0        0

        slot ptr   len   flg
        1    24    80    0
        2    104   80    0
        3    184   80    0
        4    264   80    0
        5    344   80    0
...
        30   2344  80    0
        31   2424  80    0
        32   2504  80    0
        33   2584  106   0

From the secondary:
oncheck -pp 3145732 13
addr             stamp    chksum nslots flag type         frptr
frcnt next     p
rev
3:140            607906   4624   33     881  DATA         2664
1296  0        0

        slot ptr   len   flg
        1    24    80    0
        2    104   80    0
        3    184   80    0
        4    264   80    0
        5    344   80    0
...
        30   2344  80    0
        31   2424  80    0
        32   2504  80    0
        33   2584  80    0

So slot 33 on the page is 106 bytes on the primary, but it's 80
bytes on the secondary.

This type of pages out of sync problem can cause problems if the
servers have to reverse types (so secondary becomes primary)
because now the page on the new primary thinks there is more
space available on the page then on the new secondary and so if
pages get enough out of sync that an extra slot can fit on 1
page vs the other, it can then lead to 1 of 2 types of failures.

Type 1:

Assertion failure with failed log record apply
Log record (OLDRSAM:HDELETE) failed, partnum 0x700050 rowid
0x138c612e iserrno 111

Type 2: Assertion failures caused by bfcheck error
 bfcheck: bad page: pg_frptr 3916 < sizeof(ifx_page_t) 24 or >
slotbeg 3900

So the bfcheck failure is showing that the page had written data
into the slot table in the 2nd type.  In the 1st assertion the
log record is failed to be applied because it can't find a slot
to delete because it was over written by data (so 2 different
ways for the same underlying problem to present itself)
Problem Summary:
****************************************************************
* USERS AFFECTED:                                              *
* Users of IDS version prior to 11.70.xC10.                    *
****************************************************************
* PROBLEM DESCRIPTION:                                         *
* WHEN RTREE NODE SPLITS AND HDR/RSS CONFIGURED, PAGES ON      *
* HDR/RSS                                                      *
* GET OUT OF SYNC WITH PRIMARY DUE TO SLOT LENGTH DIFFERENCE   *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
Local Fix:
Solution
Workaround
not known / see Local fix
Timestamps
Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :
03.06.2019
26.09.2019
31.08.2020
Problem solved at the following versions (IBM BugInfos)
Problem solved according to the fixlist(s) of the following version(s)
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