Oracle Locks FAQ

FAQ about Detecting and Resolving Locking Conflicts [ID 15476.1]
  Questions and Answers
     1. How does Oracle handle locking?
     2. How to find the resource definitions?
     3. Which lock modes are required for which table action?
     4. How compatibility of locks work
     5. Which views can be used to detect locking problems?
     6. Which tools are there to diagnostic locking issues?
     7. How to detect locking situations?
     8. How to resolve locking situations?
     9. How to resolve deadlock situations?
     10. Unusual locking problems
     11. How to use dbms_lock?
     References


Row Exclusive vs. Share - What is the difference between the following types of locks? [ID 266720.1]
     RESEARCH / REFERENCES
     EXCLUSIVE VS. SHARED
     Exclusive:
     Shared:
     ROW LEVEL LOCK
     WHEN LOCK CREATED
     ENQUEUE MECHANISM
     ROW EXCLUSIVE VS. ROW SHARE
     DETECTING LOCKS
          @$ORACLE_HOME/rdbms/admin/utllockt.sql


            select * from v$locked_object;
      
         col OS_USER_NAME head OS_USER for a7 trunc
            col ORACLE_USERNAME head ORCL_USER for a10 trunc
         select   ORACLE_USERNAME,OS_USER_NAME,OBJECT_NAME,locked_mode,session_id
            from all_objects a ,sys.V_$LOCKED_OBJECT b
            where a.OBJECT_ID=b.object_id;

     METALINK NOTES
     LOCKING BUG
  References




HOW TO FIND THE SESSION HOLDING A LIBRARY CACHE LOCK [ID 122793.1]

METHOD 1: SYSTEMSTATE ANALYSIS

  For Oracle 9.2.0.1 or higher

        $ sqlplus '/ as sysdba'
          oradebug setmypid
          oradebug unlimit
          oradebug dump systemstate 266
          wait 90 seconds
          oradebug dump systemstate 266
          wait 90 seconds
          oradebug dump systemstate 266
          quit

METHOD 2: EXAMINE THE X$KGLLK TABLE

Note:1054939.6 COMPILATION OF PACKAGE IS HANGING ON LIBRARY CACHE LOCK 

VIEW: "V$LOCK" Reference Note [ID 29787.1]

Note:1020012.6 SCRIPT TO RETURN MEDIUM DETAIL LOCKING INFO

Note:1020011.6 SCRIPT: LOW COMPLEXITY LOCKING INFO