Note_Tech

All technological notes.

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DBA - Memory Structure: User Global Area

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• DBA - Memory Structure: User Global Area
  • User Global Area

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User Global Area

• User Global Area

  • session memory for session variables
    • e.g.: logon information, and other information required by a database session.
    • Essentially, the UGA stores the session state.

• The UGA must be available to a database session for the life of the session.

• related to SGA/PGA

  • When using a dedicated server connection:
    • the UGA is stored in the PGA
    • 在 tnsname.ora 的 SERVER 参数, 默认是 DEDICATED, 此时专有的进程会分配给 user session. 此时 UGA 在 PGA 中.
  • When using a shared server connection:
    • the UGA is stored in the SGA, because the UGA cannot be stored in the PGA that is specific to a single process.
    • 当连接是分享时,因为 PGA 是进程独享, 不能保证完整的 session 生命周期,所以只能在 SGA

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