ORA-22924 snapshot too old Error
Problem:
Ora-22924 snapshot too old error occurs in Oracle Database when a query tries to access a row that has been modified or deleted by another transaction before the query started.
Solution:
To resolve this issue, you can increase the undo retention time so that the older versions of the data required by the query are preserved. This can be done by setting the UNDO_RETENTION parameter in the initialization parameter file. Additionally, you can use the COMMIT option in the query to explicitly commit the transaction, thereby freeing up the undo space used by the transaction. Another solution is to use the FLASHBACK query feature to retrieve the older version of the data required by the query.
Example
Here’s an example to help explain the “ora-22924 snapshot too old” error and how to resolve it.
Suppose you have a table named “customers” in your Oracle Database with the following data:IDNAMEADDRESS1AliceNew York2BobLondon
Now, assume that you start a transaction and execute the following query to retrieve the data for customer with ID 1:
SELECT * FROM customers WHERE ID = 1;
While the transaction is still active, another transaction updates the data for customer with ID 1:
UPDATE customers SET NAME = ‘Charlie’ WHERE ID = 1;
If you try to commit the first transaction now, you will get the “ora-22924 snapshot too old” error, because the query in the first transaction tried to access a row that has been modified by another transaction.
To resolve this issue, you can increase the undo retention time so that the older versions of the data required by the query are preserved. For example, you can add the following line to the initialization parameter file:
UNDO_RETENTION = 1800;
This sets the undo retention time to 1800 seconds (30 minutes).
Alternatively, you can use the COMMIT option in the query to explicitly commit the transaction, freeing up the undo space used by the transaction. For example:
SELECT /*+ COMMIT */ * FROM customers WHERE ID = 1;
Another solution is to use the FLASHBACK query feature to retrieve the older version of the data required by the query. For example:
SELECT * FROM customers AS OF TIMESTAMP (SYSTIMESTAMP – NUMTODSINTERVAL(30,’MINUTE’) WHERE ID = 1;
This retrieves the data for customer with ID 1 as it was 30 minutes ago.
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