PPT Slide

Options for Runtime Control Block

• Copying DBUX and DBU

• Sharing DBUX and DBU

• Pros for Sharing

  • The key concept for thread is sharing, so does DBU
  • Share DBU will share open files
  • Share DBU will share current record pointers

• Cons for Sharing

  • Need mechanism to control the currency of XM and locking in DBU
  • Need space control procedures to handle DBU trailer area
  • Need extra space for log record belongs to different PIN
  • Break the coherency among the DBOPEN, “accessor entry” and DBU

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