A description of the show sga results Total System Global Area AAAAA bytes Fixed Size BBBBB bytes Variable Size CCCCC bytes Database Buffers DDDDD bytes Redo Buffers EEEEE bytes fixes size: may not be the same as under the oracle of different platforms and different versions, but for the determination of the environment is a fixed The value, the information of the SGA partial components, can be seen as the area of the boot to establish SGA, including Shared Pool, Java Pool, Large Pool, Managing DB_BLOCK_BUFFERS, Manage Control File Information Memory, etc. Other management And control the memory of Oracle internal structure REDO BUFFER 分 1: Setting parameters SQL> show parameters log_buffer name type value -------------------------------------------------------------------------------------------------------------------------------------- -------- ---------------------------------- Log_Buffer Integer 524288 2: Log memory size SQL> SELECT * from V $ SGASTAT WHERE NAME LIKE '% Log%'; pool name bytes -------------------------- ---------- ---------- log_buffer 656384 3: In order to protect the log memory, add auxiliary memory, which is the protection page SQL> show SGA Total System Global Area 49604955 BYtes Fixed Size Size 109051904 BYtes Database Buffers 385875968 BYtes 385875968 BYtes 385875968 BYtes 28875968 BYTES SQL> For database If the step size is increased (for example, it may be 65K, 128K, 512K, 641K .... When the setting parameter is a value, the actual size of the database selection is greater than MIN (R) equal to this value. According to this set, if you set up log_buffer = 600k, then actually select 641 K. Then, when the memory is actually allocated, in order to do some protection to log buffer, a small part of the space is also assigned, usually 11 K size. Then there is 641 11 = 652 k, this is the last real memory size, that is, Show SGA display size
