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Function documentation Analyze Log Information Locate the document in its SAP Library structure

Use

After a system failure you have to restore your database instance or perform a restart. In the first step, the database system determines all information so you can repeat transactions since the last savepoint.

Activities

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       1.      The redo log manager starts the log reader.

       2.      The log reader reads the transaction file that was saved with the last savepoint.

       3.      The log reader recreates the transaction list using the transaction file.

       4.      For transactions that were started after the last savepoint, the log reader queries the necessary redo log entries from the log redo management or the backup manager and writes them from the log area to a redo log file.

       5.      The log reader then enters these transactions in the redo list. The log reader determines the transactions that have to be entered in the redo list in the following way:

¡        If transactions in the transaction list are marked as completed at the time of the savepoint, then the log reader enters these transactions immediately in the redo list.

¡        For each additional transaction that is found in the redo log entries, the log reader creates a redo log file. If it finds a COMMIT or a ROLLBACK for the whole transaction, then it enters the transaction in the redo list. If it finds a ROLLBACK within a transaction, then it removes the corresponding redo log entries from the redo log file to avoid these log entries from being processed unnecessarily.

¡        If the log reader does not find completed transactions after reading all redo log entries, then it flags these transactions for a ROLLBACK and enters them in the redo list. These transactions are later processed as ROLLBACK transactions.

This graphic is explained in the accompanying text

 

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