Starting with release 2021, you have an alternative option called Enterprise Organizational Management. Up until release 2021 you could only use the “legacy” organizational model in SAP S/4HANA Service that you might still know from SAP CRM. If batch scripts are started without this option, processing of the SQL statement sequence continues despite the error, it could lead to incorrect results and should be avoided.įor more information about transaction conflicts, see Transaction Conflicts for Mixed Read/Write Transactions.To process service transactions in SAP S/4HANA Service, you must set up an organizational model to map the sales and service organizations that are relevant for the service processes including the related integration into logistics, billing, and cost allocation. This causes the SQL script to be aborted if an error occurs during an automatic rollback after a transaction conflict. If the autocommit mode is disabled, the option -x in the EXAplus console is recommended. Therefore, you can disable this option with the command SET AUTOCOMMIT OFF.ĪUTOCOMMIT=OFF increases the risk of collisions and can affect other users negatively. This is true if intermediate tables, which are not intended to be saved persistently, are computed in scripts. However, for the parts that affect the performance of the system, it is better to not run a COMMIT after each SQL statement. In AUTOCOMMIT mode, successfully completed SQL statements are automatically saved persistently. To minimize the risk of transaction conflicts during parallel access by multiple users, the interfaces to Exasol (drivers) have the option AUTOCOMMIT=ON set by default. In contrast, the Exasol TMS does not conceal transactions from the user and does not persistently store statements in the database automatically. For example, it cannot undo the schema statement that has been executed. This reduces the risk of a collision when simultaneously executing transactions with schema statements, but has the disadvantage of a rollback. For example, the system may directly store schema statements ( CREATE SCHEMA or CREATE TABLE) persistently in the database. Some of the other database systems have only partially implemented the transaction model and sometimes conceal transactions from the user. In this case, you can repeat the transaction later. The transaction cannot be completed due to collisions with other transactions and is rolled back.The transaction runs till the end, but waiting times occur due to a requirement to wait for other transactions to finish.This means that two transactions cannot simultaneously update different rows of a table.ĭue to the TMS, for each transaction that is started, you will have one of the following scenarios: The granularity of the lock procedure always surrounds an entire database object, for example, one schema or one table. The individual transactions are isolated from one another by the TMS by a lock procedure. It allows the system throughput (number of fully executed transactions per unit of time) to be significantly increased compared to databases with "SingleCopy format". This keeps multiple versions of every database object (temporarily). To keep the number of colliding transactions as low as possible, Exasol supports the "MultiCopy Format". The information about occurring transaction conflicts is available in system tables EXA_USER_IMPERSONATION_LAST_DAY and EXA_DBA_TRANSACTION_CONFLICTS. If necessary, the TMS intervenes and automatically rectifies conflicts through the enforcement of waiting times or by rolling back transactions in the event of a collision. To ensure compliance with the ACID principles, every transaction is subject to an evaluation by the TMS. Transaction collisions for mixed read/write transactions, which results in a forced rollback of a transaction.Transactions must wait for a commit from an earlier transaction before it can continue.Serialization helps ensure data consistency, but can also lead to some issues, such as: This indicates that each transaction is carried out as if it was a part of a sequence even though transactions can run in parallel. Durability: All changes to a completed transaction confirmed with COMMIT remain intact.Įxasol supports the Serializable transaction isolation level.Isolation: The transaction is executed as if it is the only transaction in the system.Consistency: The transaction is given the internal consistency of the database. ![]() Atomicity: The transaction is either fully executed or not at all.To ensure this, the transaction must comply with ACID principles: Each transaction returns a correct result and leaves the database in a consistent state. A transaction-based system ensures the maintenance of complete transaction security.
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