SQL> desc x$targetrba
 Name
 -----------------------------------------
 ADDR                               N/A

 INDX                               N/A

 INST_ID                            N/A

 TOTALLOGSZ                         select sum(bytes)/redo_standard_size from v$log

 LGLOGSZ                            select bytes/512 from v$Log where status='CURRENT'

 CUR_EST_RCV_READS                  Number of dirty buffers in the buffer cache.
                                    In the Standard Edition, this column is always null.       

 ACTUAL_REDO_BLKS                   Current actual number of redo blocks required for recovery           

 TARGET_RBA_SEQ                     target redo block address log sequence    

 TARGET_RBA_BNO                     target redo block address block number

 TARGET_RBA_BOF                     target redo block address offset

 MIN_LAG                            Current target number of redo blocks that must be processed for recovery.
                                    This value is the minimum value of the following 3 columns,
                                    and identifies which of the 3 user-defined limits determines checkpointing.               

 LOGFILESZ                          Maximum number of redo blocks required to guarantee that a
                                    log switch does not occur before the checkpoint completes.  

 CT_LAG                             Number of redo blocks that need to be processed during
                                    recovery to satisfy the LOG_CHECKPOINT_TIMEOUT parameter.
                                    The value displayed is not meaningful unless that parameter has been set.

 CI_LAG                             Number of redo blocks that need to be processed during recovery to
                                    satisfy the LOG_CHECKPOINT_INTERVAL parameter.
                                    The value displayed is not meaningful unless that parameter has been set.

x$ktfbue:kernel transaction, file bitmap free extents,Free extent bitmap in file header for LMT (equivalent to fet$ in DMT); check dba_free_space view definition,ktfb –space/spcmgmt support for bitmapped space manipulation of files/tablespaces

KTFBFE means K[Kernel] T[Transaction] F[File] B[Bitmap] F[Free] E[Extents]

SQL>  desc x$ktfbfe;
 Name                                     
 ----------------------------------------- 
 ADDR               N/A                            
 INDX               N/A                      
 INST_ID            N/A                         
 KTFBFETSN          TS#  containing this free extent                       
 KTFBFEFNO          Relative number of the file containing the free extent                             
 KTFBFEBNO          Starting block number of the free extent                                
 KTFBFEBLKS         Size of the extent in ORACLE blocks

x$ktfbue:kernel transaction, file bitmap used extent,used extent bitmap in file header for LMT (equivalent to uet$ in DMT); check dba_extents view definition,ktfb –space/spcmgmt support for bitmapped space manipulation of files/tablespaces

KTFBUE means K[Kernel] T[Transaction] F[File] B[Bitmap] U[Used] E[Extents]

SQL> desc x$ktfbue;

Name	        Meaning
ADDR	        N/A
INDX	        N/A
INST_ID	        N/A
KTFBUESEGTSN	ts# containing this segment
KTFBUESEGFNO	Relative number of the file containing the segment header
KTFBUESEGBNO	segment header block number
KTFBUEEXTNO	Extent number
KTFBUEFNO	Relative number of the file containing the extent
KTFBUEBNO	Starting block number of the extent
KTFBUEBLKS	Size of the extent in ORACLE blocks
KTFBUECTM	commit_jtime,Commit Time of the undo in the extent expressed as Julian date
KTFBUESTT	commit_wtime,Commit Time of the undo in the extent expressed as wall clock time
KTFBUESTA	Transaction Status of the undo in the extent;1, 'ACTIVE', 2, 'EXPIRED', 3, 'UNEXPIRED', 0 for non-undo-extent

This is a summary list of X$ Table Definitions - Last revision was 7.3.2
The main purpose of this note is to show the naming conventions.

[K]ernel Layer
[2]-Phase Commit
[G]lobal [T]ransaction [E]ntry
X$K2GTE  - Current 2PC tx
X$K2GTE2 - Current 2PC tx
[C]ache Layer
[B]uffer Management
Buffer [H]ash
X$BH - Hash Table
Buffer LRU Statistics
X$KCBCBH - [C]urrent [B]uffers (buckets) - lru_statistics
X$KCBRBH - [R]ecent [B]uffers (buckets) - lru_extended
Buffer [WAIT]s
X$KCBWAIT  - Waits by block class
X$KCBFWAIT - Waits by File
[W]orking Sets - 7.3 or higher
X$KCBWDS - Set [D]escriptors
[C]ontrol File Management
[C]ontrol [F]ile List - 7.0.16 or higher
X$KCCCF - Control File Names & status
[D]atabase [I]nformation
X$KCCDI - Database Information
Data [F]iles
X$KCCFE - File [E]ntries ( from control file )
X$KCCFN - [F]ile [N]ames
[L]og Files
X$KCCLE - Log File [E]ntries
X$KCCLH - Log [H]istory ( archive entries )
Thread Information
X$KCCRT - [R]edo [T]hread Information
[F]ile Management
X$KCFIO - File [IO] Statistics
[L]ock Manager Component ( LCK )
[H]ash and Bucket Tables - 7.0.15 to 7.1.1, and 7.2.0 or higher
X$KCLFH - File [H]ash Table
X$KCLFI - File Bucket Table
X$LE - Lock [E]lements
X$LE_STAT - Lock Conversion [STAT]istics
X$KCLFX - Lock Element [F]ree list statistics - 7.3 or higher
X$KCLLS - Per LCK free list statistics - 7.3 or higher
X$KCLQN - [N]ame (hash) table statistics - 7.3 or higher
[R]edo Component
[M]edia recovery  - kcra.h - 7.3 or higher
X$KCRMF - [F]ile context
X$KCRMT - [T]hread context
X$KCRMX - Recovery Conte[X]t
[F]ile read
X$KCRFX - File Read Conte[X]t -  7.3 or higher
Reco[V]ery Component
[F]ile [H]eaders
X$KCVFH - All file headers
X$KCVFHMRR - Files with [M]edia [R]ecovery [R]equired
X$KCVFHONL - [ONL]ine File headers
[K]ompatibility Management - 7.1.1 or higher
X$KCKCE - [C]ompatibility Segment [E]ntries
X$KCKTY - Compatibility [TY]pes
X$KCKFM - Compatibility [F]or[M]ats ( index into X$KCKCE )
[D]ata Layer
Sequence [N]umber Component
X$KDNCE - Sequence [C]ache [E]ntries - 7.2 or lower
[S]equence Enqueues - common area for enqueue objects
X$KDNSSC - [C]ache Enqueue Objects - 7.2 or lower
X$KDNSSF - [F]lush Enqueue Objects - 7.2 or lower
X$KDNST - Cache [ST]atistics - 7.2 or lower
Inde[X] Block Component
X$KDXHS - Index [H]i[S]togram
X$KDXST - Index [ST]atistics
[G]eneric Layer
[H]eap Manager
X$KGHLU - State (summary) of [L]R[U] heap(s) - defined in ksmh.h
[I]nstantiation Manager
[C]ursor [C]ache
X$KGICC - Session statistics - defined in kqlf.h
X$KGICS - System wide statistics - defined in kqlf.h
[L]ibrary Cache Manager  ( defined and mapped from kqlf )
Bind Variables
X$KKSBV - Library Object [B]ind [V]ariables
Object Cache
X$KGLOB - All [OB]jects
X$KGLTABLE   - Filter for [TABLE]s
X$KGLBODY    - Filter for [BODY] ( packages )
X$KGLTRIGGER - Filter for [TRIGGER]s
X$KGLINDEX   - Filter for [INDEX]es
X$KGLCLUSTER - Filter for [CLUSTER]s
X$KGLCURSOR  - Filter for [CURSOR]s
Cache Dependency
X$KGLDP - Object [D]e[P]endency table
X$KGLRD - [R]ead only [D]ependency table - 7.3 or higher
Object Locks
X$KGLLK - Object [L]oc[K]s
Object Names
X$KGLNA - Object [NA]mes (sql text)
X$KGLNA1 - Object [NA]mes (sql text) with newlines - 7.2.0 or higher
Object Pins
X$KGLPN - Object [P]i[N]s
Cache Statistics
X$KGLST - Library cache [ST]atistics
Translation Table
X$KGLTR - Address [TR]anslation
Access Table
X$KGLXS - Object Access Table
Authorization Table - 7.1.5 or higher
X$KGLAU - Object Authorization table
Latch Cleanup - 7.0.15 or higher
X$KGLLC - [L]atch [C]leanup for Cache/Pin Latches
[K]ompile Layer
[S]hared Objects
X$KKSAI - Cursor [A]llocation [I]nformation - 7.3.2 or higher
[L]oader
[L]ibrary
X$KLLCNT - [C]o[NT]rol Statistics
X$KLLTAB - [TAB]le Statistics
[M]ulti-Threaded Layer
[C]ircuit component
X$KMCQS - Current [Q]ueue [S]tate
X$KMCVC - [V]irtual [C]ircuit state
[M]onitor Server/dispatcher
[D]ispatcher
X$KMMDI - [D]ispatcher [I]nfo (status)
X$KMMDP - [D]ispatcher Config ( [P]rotocol info )
[S]erver
X$KMMSI - [S]erver [I]nfo ( status )
X$KMMSG - [SG]a info ( global statistics)
X$KMMRD - [R]equest timing [D]istributions
s[Q]l Version and Option Layer
Kernel [V]ersions
X$VERSION - Library versions
Kernel [O]ptions - 7.1.3 or higher
X$OPTION - Server Options
[Q]uery Layer
[D]ictionary Cache Management
X$KQDPG - [PG]a row cache cursor statistics
[F]ixed Tables/views Management
X$KQFCO - Table [CO]lumn definitions
X$KQFDT - [D]erived [T]ables
X$KQFSZ - Kernel Data structure type [S]i[Z]es
X$KQFTA - Fixed [TA]bles
X$KQFVI - Fixed [VI]ews
X$KQFVT - [V]iew [T]ext definition - 7.2.0 or higher
[R]ow Cache Management
X$KQRST - Cache [ST]atistics
X$KQRPD - [P]arent Cache [D]efinition - 7.1.5 or higher
X$KQRSD - [S]ubordinate Cache [D]efinition - 7.1.5 or higher
[S]ervice Layer
[B]ackground Management
[D]etached Process
X$KSBDD - Detached Process [D]efinition (info)
X$KSBDP - Detached [P]rocess Descriptor (name)
X$MESSAGES - Background Message table
[I]nstance [M]anagement - 7.3 or higher
X$KSIMAT - Instance [AT]tributes
X$KSIMAV - [A]ttribute [V]alues for all instances
X$KSIMSI - [S]erial and [I]nstance numbers
[L]ock Management
[E]vent Waits
X$KSLED - Event [D]escriptors
X$KSLEI - [I]nstance wide statistics since startup
X$KSLES - Current [S]ession statistics
[L]atches
X$KSLLD - Latch [D]escriptor (name)
X$KSLLT - Latch statistics [ + Child latches @ 7.3 or higher ]
X$KSLLW - Latch context ( [W]here ) descriptors - 7.3 or higher
X$KSLPO - Latch [PO]st statistics - 7.3 or higher
X$KSLWSC- No[W]ait and [S]leep [C]ount stats by Context -7.3 or higher
[M]emory Management
[C]ontext areas
X$KSMCX - E[X]tended statistics on usage - 7.3.1 or lower
Heap Areas
X$KSMSP - SGA Hea[P]
X$KSMPP - [P]GA Hea[P] - 7.3.2 and above
X$KSMUP - [U]GA Hea[P] - 7.3.2 and above
X$KSMHP - Any [H]ea[P] - 7.3.2 and above
X$KSMSPR- [S]hared [P]ool [R]eserved List - 7.1.5 or higher
[L]east recently used shared pool chunks
X$KSMLRU - LR[U] flushes from the shared pool
[S]GA Objects
X$KSMSD - Size [D]efinition for Fixed/Variable summary
X$KSMSS - Statistics (lengths) of SGA objects
SGA [MEM]ory
X$KSMMEM - map of the entire SGA - 7.2.0 or higher
X$KSMFSV - Addresses of [F]ixed [S]GA [V]ariables - 7.2.1 or higher
[P]arameter Component
X$KSPPI  - [P]arameter [I]nfo ( Names )
X$KSPPCV - [C]urrent Session [V]alues - 7.3.2 or above
X$KSPPSV - [S]ystem [V]alues - 7.3.2 or above
En[Q]ueue Management
X$KSQDN - Global [D]atabase [N]ame
X$KSQEQ - [E]n[Q]ueue Object
X$KSQRS - Enqueue [R]e[S]ource
X$KSQST - Enqueue [S]tatistics by [T]ype
[U]ser Management
[C]ost
X$KSUCF - Cost [F]unction (resource limit)
[L]icence
X$KSULL - Licence [L]imits
[L]anguage Manager
X$NLS_PARAMETERS - NLS parameters
X$KSULV - NLS [V]alid Values - 7.1.2 or higher
[MY] [ST]atistics
X$KSUMYSTA - [MY] [ST]atisics (current session)
[P]rocess Info
X$KSUPL - Process (resource) [L]imits
X$KSUPRLAT - [LAT]ch Holder
X$KSUPR - Process object
[R]esource
X$KSURU - Resource [U]sage
[S]tatistics
X$KSUSD - [D]escriptors (statistic names)
X$KSUSGSTA - [G]lobal [ST]atistics
[SE]ssions
X$KSUSECST - Session status for events
X$KSUSESTA - Session [STA]tistics
X$KSUSECON - [CON]nection Authentication - 7.2.1 or higher
X$KSUSE - [SE]ssion Info
X$KSUSIO - [S]ystem [IO] statistics per session
[T]imer
X$KSUTM - Ti[M]e in 1/100th seconds
Instance [X]
X$KSUXSINST - [INST]ance state
[T]race management
X$TRACE - Current traced events
X$TRACES - All possible traces
X$KSTEX - Code [EX]ecution - 7.2.1 or higher
E[X]ecution Management
Device/Node [A]ffinity - 7.3.2 and above
X$KSXAFA - Current File/Node Affinity
[T]ransaction Layer
Table [A]ccess [D]efinition
X$KTADM - D[M]L lock
[C]ontrol Component
X$KTCXB - Transaction O[B]ject
[S]or[T] Segments - 7.3 or higher
X$KTSTSSD - [S]ort [S]egment [D]escriptor - per tablespace statistics
[T]ablespace
X$KTTVS - [V]alid [S]aveundo
[U]ndo
X$KTURD - Inuse [D]escriptors
X$KTUXE - Transaction [E]ntry (table) - 7.3.2 or above
Performance Layer [V] - 7.0.16 or higher
[I]nformation tables
X$KVII - [I]nitialisation Instance parameters
X$KVIS - [S]izes of structure elements
X$KVIT - [T]ransitory Instance parameters
Security Layer [Z]
[D]ictionary Component
X$KZDOS - [OS] roles
[S]ecurity State
X$KZSPR - Enabled [PR]ivileges
X$KZSRO - Enabled [RO]les
[R]emote Logins - 7.1.1 or higher
X$KZSRT - [R]emote Password File [T]able entries
E[X]ecution Layer
Parallel Query (Execute [F]ast) - 7.1.1 or higher
[P]rocess and Queue Manager
Statistics - 7.1.3 or higher
X$KXFPYS - S[YS]tem Statistics
X$KXFPDP - [D]etached [P]rocess (slave) statistics
X$KXFQSROW - Table [Q]ueue Statistics - 7.3.2 or higher
[C]oordinator Component
X$KXFPCST - Query [ST]atistics
X$KXFPCMS - [M]essage [S]tatistics
X$KXFPCDS - [D]equeue [S]tatistics
[S]lave Component
X$KXFPSST - Query [ST]atistics
X$KXFPSMS - [M]essage [S]tatistics
X$KXFPCDS - [D]equeue [S]tatistics
[S]hared Cursor
X$KXSBD - [B]ind [D]ata - 7.3.2 and above
X$KXSCC - SQL [C]ursor [C]ache Data - 7.3.2 and above
[N]etwork Layer - 7.0.15 or higher
Network [CO]nnections
X$UGANCO - Current [N]etwork [CO]nnections