HTML OPTIMIZER SAME HTML SELECT UPDATE

The Job Scheduler decides how many jobs to execute concurrently and how many to queue. The database runs as many concurrent jobs as possible. Oracle Database Resource Manager (the Resource Manager)Įnable concurrent statistics gathering by setting the CONCURRENT preference with DBMS_STATS.SET_GLOBAL_PREF. Oracle Database employs multiple tools and technologies to create and manage multiple statistics gathering jobs concurrently. The Note in the preceding execution plan shows that the database used dynamic statistics for the SELECT statement. dynamic statistics used for this statement (level=2) | Id | Operation | Name | Rows | Cost (%CPU)| Time | SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY_CURSOR)

You run the following commands (partial output included): SET LINESIZE 150 To delete and the lock optimizer statistics:Ĭonnect to the database as user oe, and then delete the statistics for the oe table.įor example, execute the following procedure: BEGINĭBMS_STATS.DELETE_TABLE_STATS('OE','ORDERS') ĭBMS_STATS.LOCK_TABLE_STATS('OE','ORDERS') įor example, use the following statement: SELECT COUNT(order_id) FROM orders The DBA_TABLES.SAMPLE_SIZE column indicates the actual sample size used to gather statistics. The statistics computed using this technique are deterministic. This algorithm reads all rows and produces statistics that are nearly as accurate as statistics from a 100% sample. This setting enables the use of the following:Ī hash-based algorithm that is much faster than sampling In this case, Oracle Database chooses the sample size automatically. To maximize performance gains while achieving necessary statistical accuracy, Oracle recommends that the ESTIMATE_PERCENT parameter use the default setting of DBMS_STATS.AUTO_SAMPLE_SIZE. The challenge is determining a sample size that provides accurate statistics in a reasonable time.ĭBMS_STATS uses sampling when a user specifies the parameter ESTIMATE_PERCENT, which controls the percentage of the rows in the table to sample. However, larger sample sizes increase the time of statistics gathering operations. The database gathers the most accurate statistics when it processes all rows in the table, which is a 100% sample. The output shows that the high-frequency job executed twice, and the standard automatic statistics collection job executed once: ID ORIGIN STATUS BEGIN_TIME END_TIME COMP FAIL TIMEO INPROħ90 HIGH_FREQ_AUTO_TASK COMPLETE 03/10 14:54:02 03/10 14:54:35 338 3 0 0ħ93 HIGH_FREQ_AUTO_TASK COMPLETE 03/10 14:58:11 03/10 14:58:45 193 3 0 0ħ94 AUTO_TASK COMPLETE 03/10 15:00:02 03/10 15:00:20 52 3 0 0 TIMED_OUT AS TIMEOUT, IN_PROGRESS AS INPROG

TO_CHAR(END_TIME, 'DD/MM HH24:MI:SS') AS END_TIME, COMPLETED, FAILED, SELECT OPID, ORIGIN, STATUS, TO_CHAR(START_TIME, 'DD/MM HH24:MI:SS' ) AS BEGIN_TIME, Wait for a few minutes, and then query the data dictionary: COL OPID FORMAT 9999 The preceding PL/SQL programs enable high-frequency collection, set the maximum run time to 3 minutes, and set the task execution interval to 4 minutes. The preceding output shows that the statistics are not stale for customers but are stale for sales.Ĭonfigure high-frequency automatic optimizer statistics collection:ĮXEC DBMS_STATS.SET_GLOBAL_PREFS('AUTO_TASK_STATUS','ON') ĮXEC DBMS_STATS.SET_GLOBAL_PREFS('AUTO_TASK_MAX_RUN_TIME','180') ĮXEC DBMS_STATS.SET_GLOBAL_PREFS('AUTO_TASK_INTERVAL','240') Query the table statistics again (sample output included): SELECT TABLE_NAME, PARTITION_NAME, NUM_ROWS, STALE_STATS Save the optimizer statistics to disk: EXEC DBMS_STATS.FLUSH_DATABASE_MONITORING_INFO The total number of sales rows increased by 100%, but only 1 row was added to customers. INSERT INTO sh.customers(cust_id, cust_first_name, cust_last_name,Ĭust_gender, cust_year_of_birth, cust_main_phone_number,Ĭust_street_address, cust_postal_code, cust_city_id,Ĭust_city, cust_state_province_id, cust_state_province,

HTML OPTIMIZER SAME HTML SELECT UPDATE

UPDATE sh.sales SET amount_sold = amount_sold + 1 WHERE amount_sold > 100 INSERT INTO sh.sales SELECT * FROM sh.sales The preceding output shows that none of the statistics are stale. SELECT TABLE_NAME, PARTITION_NAME, NUM_ROWS, STALE_STATS Query the data dictionary for the statistics for the sales and customers tables (sample output included):

Html optimizer same html select