Issues that Oracle uses to build indexes in parallel

When we build an index, we add parallelism and parallel to the index, and this column index will be parallel. When accessing an index with a degree of parallelism, the CBO may consider parallel execution, which may cause problems such as using parallelism when server resources are strained to cause more serious contention. When you use parallelism, you need to change the degree of parallelism back.

sql> drop table test purge;

sql> create TABLE test as SELECT * from Dba_objects;
sql> CREATE index ind_t_object_id on test (object_id) parallel 4;
Sql> Select S.degree
      from dba_indexes s
     where s.index_name = Upper (' Ind_t_object_id ');
Degree
----------------------------------------
4

sql> Alter index ind_t_object_id Noparallel;

Sql> Select S.degree
      from dba_indexes s
     where s.index_name = upp ER (' ind_t_object_id ');
Degree
----------------------------------------
1