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by Craig Shallahamer Get the book here |
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Craig Shallahamer's Blog
The text below is an except from the book, Oracle Performance Firefighting, written by Craig Shallahamer of OraPub, Inc. Figures and tables are not included on this page, only their reference. To order the book in either print or PDF form, click here. ©2009, 2010 by Craig Shallahamer. This is copyrighted material. Please—Out of respect for those involved in the creation of the book and also for their familes, we ask you to respect the copyright both in intent and deed. Thank you. ------------------------------- Figure 6-37. Shown is a data block (1,75847) dumped in the midst of three concurrent transactions. There are three active transactions updating a total of four rows. * Xid: This is the transaction ID, which is a concatenation of the transaction table ID (in Figure 6-37, 0003), the transaction's transaction table's slot number (in Figure 6-37, 00d), and the sequence number (in Figure 6-37, 0000318). The transaction ID is important, as it is used to ensure seemingly related undo information is truly related. * Uba: This is the undo block address. This points directly to the transaction's most recent change undo and is necessary for rolling back a transaction and also for read consistency (cloned buffer construction) purposes. Please—Out of respect for those involved in the creation of the book and also for their familes, we ask you to respect the copyright both in intent and deed. Thank you. |
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