IT21014: ONCHECK -CI REPORTS INDEX CORRUPTION ON INDEX AFTER ALTER TABLE ADD PRIMARY KEY CONSTRAINT COMMAND RUN

APAR status

• Closed as duplicate of another APAR.

Error description

• This is a very specific issue.  To encounter the problem, the
  instance needs to have done more then 1 in-place migration,
  likely including fairly specific server versions.
  
  The issue was reproduce using the following steps:
  
  1) Initialize an instance using 7.31
  2) Create the following simple table using the listed SQL
  commands
  create table t1 (c1 int, c2 int) lock mode row;
  create unique index t1_idx1 on t1(c1);
  insert into t1 values(1,1);
  3) Do an in-place migration from 7.31 to 10 (this testing
  specifically used 10.00.FC9)
  4) After upgrade completes run the following SQL command
  alter fragment on index t1_idx init in rootdbs  (this should
  detach the index from being in table as the server created all
  indexes in 7.x but it also marks this index with a special old
  style flag indicating that this detached index is fully
  detached, meaning in the leaf pages the index key has the key
  value and then fragid/rowid/delete flag entries)
  5) Do another in-place migration up to 11.70.FC7W2
  6) After upgrade completes run the following SQL
  alter table t1 add constraint primary key(c1) constraint pk_t1;
  
  At this point, the alter table command to also mark the old
  unique index as a primary key, when it re-writes the partition
  page, it loses the special old style flag, so the server no long
  knows the index leaf pages should have fragid/rowid/delete flag
  entries, so when you run oncheck -cI, it will report errors
  trying to check the index.
  
  If the system was in this state and then upgraded to 12.10, and
  oncheck -cI was run, the server would then start throwing may
  assertions that would looks like the following.
  
  03/24/17 12:45:26  Assert Failed: Code assertion at rsbtcs.c:308
  03/24/17 12:45:26  IBM Informix Dynamic Server Version
  12.10.FC8W1
  03/24/17 12:45:26   Who: Session(7040, informix@server, 19955,
  113f64c68)
          Thread(16085, oncheckm, 113f2b0b0, 9)
          File: rsdebug.c Line: 3882
  03/24/17 12:45:26   Results:
  rowoff+BT_RIDL_FLAG_SIZE+sizeof(int4) <=
  cs->bc_slotptr+cs->bc_slotlen
  
  With a stack like this:
  
  afhandler()
  affail_interface()
  rsam_assert()
  ridl_ld_elem()
  ckfnode()
  ckfnode()
  ckfnode()
  ischeck_idx()
  fm_indexcheck()
  fmoncheck()
  doidxcheck()
  chkarg4()
  sqmain()
  startup()
  
  At this point the index could be dropped and re-created which
  would get around the issue.
  

Local fix

Problem summary

Problem conclusion

Temporary fix

Comments

• This APAR is a duplicate of IT27579
  

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

Applicable component levels