An in-depth analysis of the operation process of a transaction in the undo Series

At the beginning, we first use an experiment to introduce the transaction:

1. Sys @ ORCL>SelectXid, xidusn, xidslot, xidsqn, ubablk, ubafilFromV $Transaction;
3. No RowsSelected

The corresponding transaction information is not found. Use hr to initiate a transaction:

1. Hr @ ORCL>Select*FromP;
3. ID TEST
4. ---------------
5. 2 f
6. 3g
7. 1
8. Hr @ ORCL>UpdatePSetTest ='W' WhereId = 1;
10. 1 row updated.

View transaction information again:

1. Sys @ ORCL>/
3. XID XIDUSN XIDSLOT XIDSQN UBABLK UBAFIL
4. ------------------------------------------------------------------
5. 02000800E2010000 2 8 482 3339 2

View the rollback segments of the hr initiating firm:

1. Sys @ ORCL>SelectXidusn, sid, usernameFromV $TransactionT, v $ session sWhereT. ses_addr = s. saddr;
3. XIDUSN SID USERNAME
4. --------------------------------------------------
5. 2 141 HR
6. 9 158 SCOTT

View the segment name of rollback segment 2:

1. Sys @ ORCL>Select*FromV $ rollname;
3. USNNAME
4. ----------------------------------------
5. 0 SYSTEM
6. 1 _ SYSSMU1 $
7. 2 _ SYSSMU2 $
8. 3 _ SYSSMU3 $
9. 4_syssmu4 $
10. 5_syssmu5 $
11. 6_syssmu6 $
12. 7 _ SYSSMU7 $
13. 8_syssmu8 $
14. 9 _ SYSSMU9 $
15. 10 _ SYSSMU10 $
17. 11RowsSelected.

Then dump the segment header of the rollback segment No. 2 to the udump directory:

1. Sys @ ORCL>SelectHeader_block, header_fileFromDba_segmentsWhereSegment_name ='_ SYSSMU2 $';
3. HEADER_BLOCK HEADER_FILE
4. -----------------------
5. 41 2
7. Sys @ ORCL>AlterSystem dump undo header'_ SYSSMU2 $';
9. System altered.
10. View the process ID of the server process in the current session:
11. Sys @ ORCL>SelectSpidFromV $ processWhereAddrIn(SelectPaddrFromV $ sessionWhereSid = (SelectSidFromV $ mystatWhereRownum = 1 ));
13. SPID
14. ------------
15. 5446

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