PX Deq Credit: send blkd wait event in AWR

• PX Deq Credit: send blkd 
  
  
  • The PX Deq Credit: send blkd is an idle event in a parallel execution wait event for RAC. 
  • It may happen that several Object  in schema were defined that "degree of parallelism’ different from 1.
  • Use of Oracle parallel queries may cause optimized to choose ‘full table scan’ and ‘hash join’ instead of index access and ‘nested loops join’.
  • So, parallelism is not usually employed in OLTP systems. You can alter all those objects with NOPARALLEL option.
  
  
  You can check it in any DB with the following queries:
  SELECT TABLE_NAME FROM USER_TABLES WHERE TRIM(DEGREE) <> '1' ORDER BY 1;
  SELECT INDEX_NAME FROM USER_INDEXES WHERE TRIM(DEGREE) <> '1' ORDER BY 1;