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Feature | Command Line | Description |
Enable parallel query | SELECT /*+PARALLEL(x)*/ ... FROM ...; | x indicates the parallelism for the SQL statement, which should be greater than 0. |
Disable parallel query | SELECT /*+PARALLEL(x)*/ ... FROM ...; | If x is set to 0, it indicates to disable parallel query. |
Specify the parallel table | You can specify the table to be included in or excluded from the parallel query execution plan in either of the following ways: Specify the table to be included in the plan through PARALLEL. SELECT /*+PARALLEL(t)*/ ... FROM ...;Specify the table to be excluded from the plan through NO_PARALLEL. SELECT /*+NO_PARALLEL(t)*/ ... FROM ...; | t is the table name. |
Specify both the parallel table and parallelism | SELECT /*+PARALLEL(t x)*/ * ... FROM ...; | x indicates the parallelism for the SQL statement, which should be greater than 0. t is the table name. |
Set the session parameter through the HINT statement, which takes effect only for the specified SQL statement | SELECT /*+SET_VAR(var=n)*/ * ... FROM ...; | var is the parallel query parameter in the session scope. |
select /*+PARALLEL()*/ * FROM t1,t2;
Set the parallelism to the value of txsql_parallel_degree (default) for the parallel query. If a statement does not meet the parallel query execution condition, serial query will be used.select /*+PARALLEL(4)*/ * FROM t1,t2;
Set the parallelism of the statement to 4 regardless of the default value, i.e., txsql_parallel_degree = 4. If the statement does not meet the parallel query execution condition, serial query will be used.select /*+PARALLEL(t1)*/ * FROM t1,t2;
Include the t1 table in the parallel query and use the default parallelism. If t1 is smaller than the value of txsql_parallel_table_record_threshold, serial query will be used.select /*+PARALLEL(t1 8)*/ * FROM t1,t2;
Include the t1 table in the parallel query and set the parallelism to 8. If t1 is smaller than the value of txsql_parallel_table_record_threshold, serial query will be used.select /*+NO_PARALLEL(t1)*/ * FROM t1,t2;
Exclude the t1 table from the parallel query. If t1 is greater than the value of txsql_parallel_table_record_threshold, serial query will be used.select /*+SET_VAR(txsql_parallel_degree=8)*/ * FROM t1,t2;
Set the parallelism of the statement to 8 regardless of the default value, i.e., txsql_parallel_degree = 8.select /*+SET_VAR(txsql_parallel_cost_threshold=1000)*/ * FROM t1,t2
Set txsql_parallel_cost_threshold=1000 for the statement. If its execution penalty is greater than 1000, parallel query can be used.select /*+SET_VAR(txsql_optimizer_context_max_mem_size=500000)*/ * FROM t1,t2
Set txsql_optimizer_context_max_mem_size=500000 for a statement, which means to adjust the maximum memory size it can apply for in the parallel query plan environment to 500000.Was this page helpful?
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