SQL Script for Index Recommendations and Analysis in Oracle:

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1. Generate Index Recommendations using Oracle SQL Tuning Advisor 

 Description: This script generates index recommendations using the Oracle SQL Tuning Advisor for a specific SQL statement. Replace 'SELECT /*+ YOUR_HINTS */ YOUR_COLUMNS FROM YOUR_TABLE WHERE YOUR_CONDITIONS;' with the actual SQL statement you want to tune. The script creates a tuning task for the provided SQL statement and executes it. The task_name variable will display the name of the tuning task generated.

-- Generate index recommendations using the SQL Tuning Advisor for a specific SQL statement
DECLARE
  task_name   VARCHAR2(30);
  stmt_id     NUMBER;
BEGIN
  stmt_id := DBMS_SQLTUNE.CREATE_TUNING_TASK(
    sql_text => 'SELECT /*+ YOUR_HINTS */ YOUR_COLUMNS FROM YOUR_TABLE WHERE YOUR_CONDITIONS;',
    scope    => DBMS_SQLTUNE.SCOPE_COMPUTE
  );

  task_name := DBMS_SQLTUNE.EXECUTE_TUNING_TASK(task_name => stmt_id);
  DBMS_OUTPUT.PUT_LINE('Task Name: ' || task_name);
END;
/

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2. Analyze Impact of Adding or Removing an Index on Query Performance Description: 

This script allows you to analyze the impact of adding or removing an index on query performance. Replace with the original query you want to analyze. Execute the script to generate the execution plan for the original query. Then, add or remove the index in question and re-run the EXPLAIN PLAN for the same query. Compare the two execution plans to understand the performance difference.

-- Query to analyze the impact of adding or removing an index on query performance
EXPLAIN PLAN FOR
<YOUR_QUERY>;

SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY);

-- Add or remove the index and re-run the EXPLAIN PLAN to compare the results

3. Identify Missing Indexes for Specific SQL Statements or Workload Description: This script identifies missing indexes for specific SQL statements or workload in the Automatic Workload Repository (AWR). Replace 'YOUR_SCHEMA_NAME' with the appropriate schema name. The script joins multiple AWR views to find SQL statements with high buffer gets and a significant number of executions that could potentially benefit from an index on the first column. These advanced scripts should help you with index recommendations and analysis in Oracle. Use them with caution, especially when making changes to production databases. Always test changes in a controlled environment before applying them to critical systems.

-- Query to identify missing indexes for specific SQL statements or workload
SELECT sql_id, sql_text, table_name, column_name
FROM dba_hist_sql_plan p
JOIN dba_hist_sqlstat s ON p.sql_id = s.sql_id AND p.plan_hash_value = s.plan_hash_value
JOIN dba_indexes i ON p.table_name = i.table_name AND p.column_name = i.column_name
WHERE i.table_owner = 'YOUR_SCHEMA_NAME'
  AND i.column_position = 1
  AND i.index_type = 'NORMAL'
  AND i.uniqueness = 'NONUNIQUE'
  AND s.buffer_gets > 10000
  AND s.executions > 10
ORDER BY sql_id;

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