• row cache lock


    SQL> col name format a30
    SQL> select * from (select SAMPLE_TIME,
           SESSION_ID,  
           NAME,  
           P1,  
           P2,  
           P3,
           ash.BLOCKING_SESSION  
      from v$active_session_history ash, v$event_name enm  
     where ash.event# = enm.event#
     and enm.NAME='row cache lock')
     where rownum<10;  2    3    4    5    6    7    8    9   10   11  
    
    SAMPLE_TIME								    SESSION_ID NAME				      P1	 P2	    P3 
    
    BLOCKING_SESSION
    --------------------------------------------------------------------------- ---------- ------------------------------ ---------- ---------- ---------- -----
    
    -----------
    15-APR-14 07.48.08.840 PM							    22 row cache lock			      13	  0	     5
    15-APR-14 07.45.49.883 PM							  1159 row cache lock			      13	  0	     5
    15-APR-14 07.44.12.569 PM							    25 row cache lock			      13	  0	     5
    
    ROW CACHE LOCK等待事件是一个共享池相关的等待事件。是由于对于字典缓冲的访问造成的。
    P1 – Cache Id
    P2 – Mode Held
    P3 – Mode Requested
    
    SQL查询
    --查询row cache lock等待
    select *  from v$session_wait where wait_class = 'row cache lock';
     
    --查询rowcache 名称
    select * from v$rowcache where cache# = &p1;
    
    
    DC_SEQUENCES
    Check for appropriate caching of sequences for the application requirements.
    
    DC_USERS
    Deadlock and resulting “WAITED TOO LONG FOR A ROW CACHE ENQUEUE LOCK!” can occur if a session issues a GRANT to a user, and that user is in the process of 
    
    logging on to the database.
    
    DC_SEGMENTS
    This is likely to be down to segment allocation. Identify what the session holding the enqueue is doing and use errorstacks to diagnose.
    
    DB_ROLLBACK_SEGMENTS
    This is due to rollback segment allocation. Just like dc_segments,identify what is holding the enqueue and also generate errorstacks. Remember that on a 
    
    multi-node system (RAC) the holder may be on another node and so multiple systemstates from each node will be required.
    
    DC_AWR_CONTROL
    This enqueue is related to control of the Automatic Workload Repository. As such any operation manipulating the repository may hold this so look for 
    
    processes blocking these.
    
    SQL> select a.cache#,a.PARAMETER from v$rowcache a where cache# =13;
    
        CACHE# PARAMETER
    ---------- --------------------------------
    	13 dc_sequences

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  • 原文地址:https://www.cnblogs.com/hzcya1995/p/13352340.html
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