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Library cache is very important part of Oracle Shared pool. Shared Pool controls execution of SQL statements. Shared pool is divided into Data dictionary Cache and Library Cache. Main component of Library cache include Shared SQL Area and Private SQL Area (in case of shared server configuration).In Dedicated server configuration Private SQL area is created in PGA of server process. In oracle database each statement is associated with a shared area and a private area. Both are discussed in detail below. Continue reading Oracle Library Cache | Hard Parsing Vs Soft Parsing
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Oracle database keeps record of changes made to data. Every time user performs a DML, DDL or DCL operation, its redo entries are also created. These redo entries contain commands to rebuild or redo the changes. These entries are stored in Redo Log buffer. Log writer process (LGWR) writes these redo entries to redo log files. Redo log buffer works in circular fashion. It means that it overwrites old entries. Continue reading Redo Log Buffer & Log writer process (LGWR)
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Data required by oracle user process is loaded into buffer cache, if it is not already present in cache. Proper memory tuning is required to avoid repeated disk access for the same data. This means that there should be enough space in buffer cache to hold required data for long time. If same data is required in very short intervals then such data should be permanently pinned into memory. Oracle allows us to use multiple buffers. Using multiple buffers we can control that how long objects should be kept in memory.
Continue reading Keep Buffer Pool and Recycle Buffer Pool