After completing this lesson, you should be able to do the following: Monitor and size the redo log buffer Monitor and size the Java pool Control the amount of Java session memory used by a session | Sizing Other SGA Structures Objectives After completing this lesson, you should be able to do the following: Monitor and size the redo log buffer Monitor and size the Java pool Control the amount of Java session memory used by a session Database buffer cache Redo log buffer Shared pool Library cache Data dictionary cache User global area The Redo Log Buffer SQL> UPDATE employees 2 SET salary=salary* 3 WHERE employee_id=736; Server process LGWR Control files ARCn Archived log files Redo log files Data files Redo Log Buffer Content The Oracle server processes copy redo entries from the user’s memory space to the redo log buffer for each DML or DDL statement. The redo entries contain the information necessary to reconstruct or redo changes made to the database by DML and DDL operations. They are used for database recovery and take up continuous sequential space in the buffer. The redo log buffer is a circular buffer. The server processes can copy new entries over the entries in the redo log buffer that have already been written to disk. The LGWR process normally writes fast enough to ensure that space is always available in the buffer for new entries. The LGWR process writes the redo log buffer to the active online redo log file (or members of the active group) on disk. The LGWR process copies to disk all redo entries that have been entered into the buffer since the last time LGWR wrote to disk. What Causes LGWR to Write? LGWR writes out the redo data from the redo log buffer when: A user process commits a transaction Every three seconds When the redo log buffer is one-third full When a DBWn process writes modified buffers to disk, if the corresponding redo log data has not already been written to disk Sizing the Redo Log Buffer Adjust the LOG_BUFFER parameter. Default value: Either 512K or 128K * the value of CPU_COUNT, whichever is greater. Sizing the Redo Log Buffer If transactions are long or numerous, then larger values of LOG_BUFFER will reduce log file I/O. | Sizing Other SGA Structures Objectives After completing this lesson, you should be able to do the following: Monitor and size the redo log buffer Monitor and size the Java pool Control the amount of Java session memory used by a session Database buffer cache Redo log buffer Shared pool Library cache Data dictionary cache User global area The Redo Log Buffer SQL> UPDATE employees 2 SET salary=salary* 3 WHERE employee_id=736; Server process LGWR Control files ARCn Archived log files Redo log files Data files Redo Log Buffer Content The Oracle server processes copy redo entries from the user’s memory space to the redo log buffer for each DML or DDL statement. The redo entries contain the information necessary to reconstruct or redo changes made to the database by DML and DDL operations. They are used for database recovery and take up continuous sequential space in the buffer. The redo log buffer is a circular buffer. The server processes can copy new entries over the entries in the .
