Home
All Oracle Error Codes
Oracle DBA Forum

Frequent Oracle Errors

TNS:could not resolve the connect identifier specified
Backtrace message unwound by exceptions
invalid identifier
PL/SQL compilation error
internal error
missing expression
table or view does not exist
end-of-file on communication channel
TNS:listener unknown in connect descriptor
insufficient privileges
PL/SQL: numeric or value error string
TNS:protocol adapter error
ORACLE not available
target host or object does not exist
invalid number
unable to allocate string bytes of shared memory
resource busy and acquire with NOWAIT specified
error occurred at recursive SQL level string
ORACLE initialization or shutdown in progress
archiver error. Connect internal only, until freed
snapshot too old
unable to extend temp segment by string in tablespace
Credential retrieval failed
missing or invalid option
invalid username/password; logon denied
unable to create INITIAL extent for segment
out of process memory when trying to allocate string bytes
shared memory realm does not exist
cannot insert NULL
TNS:unable to connect to destination
remote database not found ora-02019
exception encountered: core dump
inconsistent datatypes
no data found
TNS:operation timed out
PL/SQL: could not find program
existing state of packages has been discarded
maximum number of processes exceeded
error signaled in parallel query server
ORACLE instance terminated. Disconnection forced
TNS:packet writer failure
see ORA-12699
missing right parenthesis
name is already used by an existing object
cannot identify/lock data file
invalid file operation
quoted string not properly terminated

RE: Unindexed FK Cause Deadlock or Only Share Lock?

Post, Ethan

2005-06-30

Replies:
I was hoping one of the more brilliant scienticians from the other side
of the pond would chime in. If I may beg you to waste a little more time
with my humble request. What happens when there is an index, and let's
assume the index only contains 2 distinct values over zillions of
records. Have we eliminated the deadlock scenario below entirely? I am
all for indexing my FK's but was not aware such a otherwise useless
index (as described in previous sentence) could be so useful?

-----Original Message-----
From: oracle-l-bounce@(protected)
[mailto:oracle-l-bounce@(protected)
Sent: Thursday, June 30, 2005 3:21 PM
To: Oracle-L@(protected))
Subject: Re: Unindexed FK Cause Deadlock or Only Share Lock?


If you attempt to delete a parent row,
or update the key value of a parent
row in a parent/child relationship where
the child DOES NOT HAVE an index
on the foreign key, then Oracle will
attempt to acquire a mode 4 lock
on the child table (or mode 5 if it
has previously modified the child
table).

If any other sessions are currently
modifying the child table, your session
will have to wait before it can acquire
its mode 4/5 as the other sessions will
be holding mode 3 and therefore will
be blocking you.

Anyone who tries to start a new transaction
on the child table (and therefore need to
acquire a mode 3) will be blocked behind
your request for a mode 4.


To engineer a deadlock:
  session A
    delete child row C1
    acquires mode 3 on child table

  session B
    delete child row C2
    acquires mode 3 on child table

  session A
    attempts to delete parent of C1
    attempts to convert mode 3 to mode 5
    blocked by session B holding mode 3
       therefore starts to wait

  session B
    attempts to delete parent of C2
    attempts to convert mode 3 to mode 5
    blocked by session A in the converters queue
       (viz: holding 3, and waiting to convert to 5)
       therefore start to wait

  Three seconds or less later, session a gets
  an ORA-00060 Deadlock detected.



Regards

Jonathan Lewis

http://www.jlcomp.demon.co.uk/faq/ind_faq.html
The Co-operative Oracle Users' FAQ

http://www.jlcomp.demon.co.uk/appearances.html
Public Appearances - schedule updated June 22nd 2005


--
http://www.freelists.org/webpage/oracle-l