v$transaction

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Important fields of v$transaction are used_ublk and used_urec. They tell of how many blocks and records the undo for a transaction consists. In order to find out the name of the corresponding rollback segemnt, join the xidusn field with the usn field of v$rollname.

 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 ADDR                                               RAW(8)
 XIDUSN                                             NUMBER
 XIDSLOT                                            NUMBER
 XIDSQN                                             NUMBER
 UBAFIL                                             NUMBER
 UBABLK                                             NUMBER
 UBASQN                                             NUMBER
 UBAREC                                             NUMBER
 STATUS                                             VARCHAR2(16)
 START_TIME                                         VARCHAR2(20)
 START_SCNB                                         NUMBER
 START_SCNW                                         NUMBER
 START_UEXT                                         NUMBER
 START_UBAFIL                                       NUMBER
 START_UBABLK                                       NUMBER
 START_UBASQN                                       NUMBER
 START_UBAREC                                       NUMBER
 SES_ADDR                                           RAW(8)
 FLAG                                               NUMBER
 SPACE                                              VARCHAR2(3)
 RECURSIVE                                          VARCHAR2(3)
 NOUNDO                                             VARCHAR2(3)
 PTX                                                VARCHAR2(3)
 NAME                                               VARCHAR2(256)
 PRV_XIDUSN                                         NUMBER
 PRV_XIDSLT                                         NUMBER
 PRV_XIDSQN                                         NUMBER
 PTX_XIDUSN                                         NUMBER
 PTX_XIDSLT                                         NUMBER
 PTX_XIDSQN                                         NUMBER
 DSCN-B                                             NUMBER
 DSCN-W                                             NUMBER
 USED_UBLK                                          NUMBER
 USED_UREC                                          NUMBER
 LOG_IO                                             NUMBER
 PHY_IO                                             NUMBER
 CR_GET                                             NUMBER
 CR_CHANGE                                          NUMBER

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