20 Monitoring Streams Capture Processes

This chapter provides sample queries that you can use to monitor Streams environment capture processes.

This chapter contains these topics:

Displaying the Queue, Rule Sets, and Status of Each Capture Process
Displaying Change Capture Information About Each Capture Process
Displaying State Change and Message Creation Time for Each Capture Process
Displaying Elapsed Time Performing Capture Operations for Each Capture Process
Displaying Information About Each Downstream Capture Process
Displaying the Registered Redo Log Files for Each Capture Process
Displaying the Redo Log Files that Are Required by Each Capture Process
Displaying SCN Values for Each Redo Log File Used by Each Capture Process
Displaying the Last Archived Redo Entry Available to Each Capture Process
Listing the Parameter Settings for Each Capture Process
Viewing the Extra Attributes Captured by Each Capture Process
Determining the Applied SCN for All Capture Processes in a Database
Determining Redo Log Scanning Latency for Each Capture Process
Determining Message Enqueuing Latency for Each Capture Process
Displaying Information About Rule Evaluations for Each Capture Process

Note:

The Streams tool in the Oracle Enterprise Manager Console is also an excellent way to monitor a Streams environment. See the online help for the Streams tool for more information.

See Also:

Chapter 2, "Streams Capture Process"
Chapter 11, "Managing a Capture Process"
Oracle Database Reference for information about the data dictionary views described in this chapter
Oracle Streams Replication Administrator's Guide for information about monitoring a Streams replication environment

Displaying the Queue, Rule Sets, and Status of Each Capture Process

You can display the following information about each capture process in a database by running the query in this section:

The capture process name
The name of the queue used by the capture process
The name of the positive rule set used by the capture process
The name of the negative rule set used by the capture process
The status of the capture process, which can be ENABLED, DISABLED, or ABORTED

To display this general information about each capture process in a database, run the following query:

COLUMN CAPTURE_NAME HEADING 'Capture|Process|Name' FORMAT A15
COLUMN QUEUE_NAME HEADING 'Capture|Process|Queue' FORMAT A15
COLUMN RULE_SET_NAME HEADING 'Positive|Rule Set' FORMAT A15
COLUMN NEGATIVE_RULE_SET_NAME HEADING 'Negative|Rule Set' FORMAT A15
COLUMN STATUS HEADING 'Capture|Process|Status' FORMAT A15

SELECT CAPTURE_NAME, QUEUE_NAME, RULE_SET_NAME, NEGATIVE_RULE_SET_NAME, STATUS 
   FROM DBA_CAPTURE;

Your output looks similar to the following:

Capture         Capture                                         Capture
Process         Process         Positive        Negative        Process
Name            Queue           Rule Set        Rule Set        Status
--------------- --------------- --------------- --------------- ---------------
STRM01_CAPTURE  STRM01_QUEUE    RULESET$_25     RULESET$_36     ENABLED

If the status of a capture process is ABORTED, then you can query the ERROR_NUMBER and ERROR_MESSAGE columns in the DBA_CAPTURE data dictionary view to determine the error.

See Also:

"Is the Capture Process Enabled?" for an example query that shows the error number and error message if a capture process is aborted

Displaying Change Capture Information About Each Capture Process

The query in this section displays the following information about each capture process in a database:

The name of the capture process.
The process number (cnnn).
The session identifier.
The serial number of the session.
The current state of the capture process:
- INITIALIZING
- WAITING FOR DICTONARY REDO
- DICTIONARY INITIALIZATION
- MINING
- LOADING
- CAPTURING CHANGES
- WAITING FOR REDO
- EVALUATING RULE
- CREATING LCR
- ENQUEUING MESSAGE
- PAUSED FOR FLOW CONTROL
- SHUTTING DOWN
The total number of redo entries passed by LogMiner to the capture process for detailed rule evaluation. A capture process converts a redo entry into a message and performs detailed rule evaluation on the message when capture process prefiltering cannot discard the change.
The total number LCRs enqueued since the capture process was last started.

To display this information for each capture process in a database, run the following query:

COLUMN CAPTURE_NAME HEADING 'Capture|Name' FORMAT A7
COLUMN PROCESS_NAME HEADING 'Capture|Process|Number' FORMAT A7
COLUMN SID HEADING 'Session|ID' FORMAT 9999
COLUMN SERIAL# HEADING 'Session|Serial|Number' FORMAT 9999
COLUMN STATE HEADING 'State' FORMAT A27
COLUMN TOTAL_MESSAGES_CAPTURED HEADING 'Redo|Entries|Evaluated|In Detail' FORMAT 9999999
COLUMN TOTAL_MESSAGES_ENQUEUED HEADING 'Total|LCRs|Enqueued' FORMAT 999999

SELECT c.CAPTURE_NAME,
       SUBSTR(s.PROGRAM,INSTR(s.PROGRAM,'(')+1,4) PROCESS_NAME, 
       c.SID,
       c.SERIAL#, 
       c.STATE,
       c.TOTAL_MESSAGES_CAPTURED,
       c.TOTAL_MESSAGES_ENQUEUED 
  FROM V$STREAMS_CAPTURE c, V$SESSION s
  WHERE c.SID = s.SID AND
        c.SERIAL# = s.SERIAL#;

Your output looks similar to the following:

Redo
        Capture         Session                               Entries    Total
Capture Process Session  Serial                             Evaluated     LCRs
Name    Number       ID  Number State                       In Detail Enqueued
------- ------- ------- ------- --------------------------- --------- --------
CAPTURE C001        964       3 CAPTURING CHANGES              189346      565

The number of redo entries scanned can be higher than the number of DML and DDL redo entries captured by a capture process. Only DML and DDL redo entries that satisfy the rule sets of a capture process are captured and enqueued into the capture process queue. Also, the total LCRs enqueued includes LCRs that contain transaction control statements. These row LCRs contain directives such as COMMIT and ROLLBACK. Therefore, the total LCRs enqueued is a number higher than the number of row changes and DDL changes enqueued by a capture process.

See Also:

"Row LCRs" for more information about transaction control statements
"Capture Process States"

Displaying State Change and Message Creation Time for Each Capture Process

The query in this section displays the following information for each capture process in a database:

The name of the capture process
The current state of the capture process:
- INITIALIZING
- WAITING FOR DICTONARY REDO
- DICTIONARY INITIALIZATION
- MINING
- LOADING
- CAPTURING CHANGES
- WAITING FOR REDO
- EVALUATING RULE
- CREATING LCR
- ENQUEUING MESSAGE
- PAUSED FOR FLOW CONTROL
- SHUTTING DOWN
The date and time when the capture process state last changed
The date and time when the capture process last created an LCR

To display this information for each capture process in a database, run the following query:

COLUMN CAPTURE_NAME HEADING 'Capture|Name' FORMAT A15
COLUMN STATE HEADING 'State' FORMAT A27
COLUMN STATE_CHANGED HEADING 'State|Change Time'
COLUMN CREATE_MESSAGE HEADING 'Last Message|Create Time'

SELECT CAPTURE_NAME,
       STATE,
       TO_CHAR(STATE_CHANGED_TIME, 'HH24:MI:SS MM/DD/YY') STATE_CHANGED,
       TO_CHAR(CAPTURE_MESSAGE_CREATE_TIME, 'HH24:MI:SS MM/DD/YY') CREATE_MESSAGE
  FROM V$STREAMS_CAPTURE;

Your output looks similar to the following:

Capture                                     State             Last Message
Name            State                       Change Time       Create Time
--------------- --------------------------- ----------------- -----------------
CAPTURE_SIMP    CAPTURING CHANGES           13:24:42 11/08/04 13:24:41 11/08/04

See Also:

"Capture Process States"

Displaying Elapsed Time Performing Capture Operations for Each Capture Process

The query in this section displays the following information for each capture process in a database:

The name of the capture process
The elapsed capture time, which is the amount of time (in seconds) spent scanning for changes in the redo log since the capture process was last started
The elapsed rule evaluation time, which is the amount of time (in seconds) spent evaluating rules since the capture process was last started
The elapsed enqueue time, which is the amount of time (in seconds) spent enqueuing messages since the capture process was last started
The elapsed LCR creation time, which is the amount of time (in seconds) spent creating logical change records (LCRs) since the capture process was last started
The elapsed pause time, which is the amount of time (in seconds) spent paused for flow control since the capture process was last started

Note:

All times for this query are displayed in seconds. The V$STREAMS_CAPTURE view displays elapsed time in centiseconds by default. A centisecond is one-hundredth of a second. The query in this section divides each elapsed time by one hundred to display the elapsed time in seconds.

To display this information for each capture process in a database, run the following query:

COLUMN CAPTURE_NAME HEADING 'Capture|Name' FORMAT A15
COLUMN ELAPSED_CAPTURE_TIME HEADING 'Elapsed|Capture|Time' FORMAT 99999999.99
COLUMN ELAPSED_RULE_TIME HEADING 'Elapsed|Rule|Evaluation|Time' FORMAT 99999999.99
COLUMN ELAPSED_ENQUEUE_TIME HEADING 'Elapsed|Enqueue|Time' FORMAT 99999999.99
COLUMN ELAPSED_LCR_TIME HEADING 'Elapsed|LCR|Creation|Time' FORMAT 99999999.99
COLUMN ELAPSED_PAUSE_TIME HEADING 'Elapsed|Pause|Time' FORMAT 99999999.99

SELECT CAPTURE_NAME,
       (ELAPSED_CAPTURE_TIME/100) ELAPSED_CAPTURE_TIME,
       (ELAPSED_RULE_TIME/100) ELAPSED_RULE_TIME,
       (ELAPSED_ENQUEUE_TIME/100) ELAPSED_ENQUEUE_TIME,
       (ELAPSED_LCR_TIME/100) ELAPSED_LCR_TIME,
       (ELAPSED_PAUSE_TIME/100) ELAPSED_PAUSE_TIME
  FROM V$STREAMS_CAPTURE;

Your output looks similar to the following:

Elapsed                   Elapsed
                     Elapsed         Rule      Elapsed          LCR      Elapsed
Capture              Capture   Evaluation      Enqueue     Creation        Pause
Name                    Time         Time         Time         Time         Time
--------------- ------------ ------------ ------------ ------------ ------------
STM1$CAP             1213.92          .04        33.84       185.25       600.60

Displaying Information About Each Downstream Capture Process

A downstream capture is a capture process runs on a database other than the source database. You can display the following information about each downstream capture process in a database by running the query in this section:

The capture process name
The source database of the changes captured by the capture process
The name of the queue used by the capture process
The status of the capture process, which can be ENABLED, DISABLED, or ABORTED
Whether the downstream capture process uses a database link to the source database for administrative actions

To display this information about each downstream capture process in a database, run the following query:

COLUMN CAPTURE_NAME HEADING 'Capture|Process|Name' FORMAT A15
COLUMN SOURCE_DATABASE HEADING 'Source|Database' FORMAT A15
COLUMN QUEUE_NAME HEADING 'Capture|Process|Queue' FORMAT A15
COLUMN STATUS HEADING 'Capture|Process|Status' FORMAT A15
COLUMN USE_DATABASE_LINK HEADING 'Uses|Database|Link?' FORMAT A8

SELECT CAPTURE_NAME, 
       SOURCE_DATABASE, 
       QUEUE_NAME, 
       STATUS, 
       USE_DATABASE_LINK
   FROM DBA_CAPTURE
   WHERE CAPTURE_TYPE = 'DOWNSTREAM';

Your output looks similar to the following:

Capture                         Capture         Capture         Uses
Process         Source          Process         Process         Database
Name            Database        Queue           Status          Link?
--------------- --------------- --------------- --------------- --------
STRM03_CAPTURE  DBS1.NET        STRM03_QUEUE    ENABLED         YES

In this case, the source database for the capture process is dbs1.net, but the local database running the capture process is not dbs1.net. Also, the capture process returned by this query uses a database link to the source database to perform administrative actions. The database link name is the same as the global name of the source database, which is dbs1.net in this case.

If the status of a capture process is ABORTED, then you can query the ERROR_NUMBER and ERROR_MESSAGE columns in the DBA_CAPTURE data dictionary view to determine the error.

See Also:

"Local Capture and Downstream Capture"
"Creating an Archived-Log Downstream Capture Process that Assigns Logs Implicitly"
"Is the Capture Process Enabled?" for an example query that shows the error number and error message if a capture process is aborted

Displaying the Registered Redo Log Files for Each Capture Process

You can display information about the archived redo log files that are registered for each capture process in a database by running the query in this section. This query displays information about these files for both local capture processes and downstream capture processes.

The query displays the following information for each registered archived redo log file:

The name of a capture process that uses the file
The source database of the file
The sequence number of the file
The name and location of the file at the local site
Whether the file contains the beginning of a data dictionary build
Whether the file contains the end of a data dictionary build

To display this information about each registered archive redo log file in a database, run the following query:

COLUMN CONSUMER_NAME HEADING 'Capture|Process|Name' FORMAT A15
COLUMN SOURCE_DATABASE HEADING 'Source|Database' FORMAT A10
COLUMN SEQUENCE# HEADING 'Sequence|Number' FORMAT 99999
COLUMN NAME HEADING 'Archived Redo Log|File Name' FORMAT A20
COLUMN DICTIONARY_BEGIN HEADING 'Dictionary|Build|Begin' FORMAT A10
COLUMN DICTIONARY_END HEADING 'Dictionary|Build|End' FORMAT A10

SELECT r.CONSUMER_NAME,
       r.SOURCE_DATABASE,
       r.SEQUENCE#, 
       r.NAME, 
       r.DICTIONARY_BEGIN, 
       r.DICTIONARY_END 
  FROM DBA_REGISTERED_ARCHIVED_LOG r, DBA_CAPTURE c
  WHERE r.CONSUMER_NAME = c.CAPTURE_NAME;

Your output looks similar to the following:

Capture                                                  Dictionary Dictionary
Process         Source     Sequence Archived Redo Log    Build      Build
Name            Database     Number File Name            Begin      End
--------------- ---------- -------- -------------------- ---------- ----------
STRM02_CAPTURE  DBS2.NET         15 /orc/dbs/log/arch2_1 NO         NO
                                    _15_478347508.arc
STRM02_CAPTURE  DBS2.NET         16 /orc/dbs/log/arch2_1 NO         NO
                                    _16_478347508.arc 
STRM03_CAPTURE  DBS1.NET         45 /remote_logs/arch1_1 YES        YES
                                    _45_478347335.arc
STRM03_CAPTURE  DBS1.NET         46 /remote_logs/arch1_1 NO         NO
                                    _46_478347335.arc
STRM03_CAPTURE  DBS1.NET         47 /remote_logs/arch1_1 NO         NO
                                    _47_478347335.arc

Assume that this query was run at the dbs2.net database, and that strm02_capture is a local capture process, and strm03_capture is a downstream capture process. The source database for the strm03_capture downstream capture process is dbs1.net. This query shows that there are two registered archived redo log files for strm02_capture and three registered archived redo log files for strm02_capture. This query shows the name and location of each of these files in the local file system.

See Also:

"The LogMiner Data Dictionary for a Capture Process" for more information about data dictionary builds
"Local Capture and Downstream Capture"
"Creating an Archived-Log Downstream Capture Process that Assigns Logs Implicitly"
"ARCHIVELOG Mode and a Capture Process"

Displaying the Redo Log Files that Are Required by Each Capture Process

A capture process needs the redo log file that includes the required checkpoint SCN, and all subsequent redo log files. You can query the REQUIRED_CHECKPOINT_SCN column in the DBA_CAPTURE data dictionary view to determine the required checkpoint SCN for a capture process. Redo log files prior to the redo log file that contains the required checkpoint SCN are no longer needed by the capture process. These redo log files can be stored offline if they are no longer needed for any other purpose. If you reset the start SCN for a capture process to a lower value in the future, then these redo log files might be needed.

The query displays the following information for each required archived redo log file:

The name of a capture process that uses the file
The source database of the file
The sequence number of the file
The name and location of the required redo log file at the local site

To display this information about each required archive redo log file in a database, run the following query:

COLUMN CONSUMER_NAME HEADING 'Capture|Process|Name' FORMAT A15
COLUMN SOURCE_DATABASE HEADING 'Source|Database' FORMAT A10
COLUMN SEQUENCE# HEADING 'Sequence|Number' FORMAT 99999
COLUMN NAME HEADING 'Required|Archived Redo Log|File Name' FORMAT A40

SELECT r.CONSUMER_NAME,
       r.SOURCE_DATABASE,
       r.SEQUENCE#, 
       r.NAME 
  FROM DBA_REGISTERED_ARCHIVED_LOG r, DBA_CAPTURE c
  WHERE r.CONSUMER_NAME =  c.CAPTURE_NAME AND
        r.NEXT_SCN      >= c.REQUIRED_CHECKPOINT_SCN;

Your output looks similar to the following:

Capture                             Required
Process         Source     Sequence Archived Redo Log
Name            Database     Number File Name
--------------- ---------- -------- ----------------------------------------
STRM02_CAPTURE  DBS2.NET         16 /orc/dbs/log/arch2_1_16_478347508.arc
STRM03_CAPTURE  DBS1.NET         47 /remote_logs/arch1_1_47_478347335.arc

See Also:

"Required Checkpoint SCN"

Displaying SCN Values for Each Redo Log File Used by Each Capture Process

You can display information about the SCN values for archived redo log files that are registered for each capture process in a database by running the query in this section. This query displays information the SCN values for these files for both local capture processes and downstream capture processes. This query also identifies redo log files that are no longer needed by any capture process at the local database.

The query displays the following information for each registered archived redo log file:

The capture process name of a capture process that uses the file
The name and location of the file at the local site
The lowest SCN value for the information contained in the redo log file
The lowest SCN value for the next redo log file in the sequence
Whether the redo log file is purgeable

To display this information about each registered archive redo log file in a database, run the following query:

COLUMN CONSUMER_NAME HEADING 'Capture|Process|Name' FORMAT A15
COLUMN NAME HEADING 'Archived Redo Log|File Name' FORMAT A25
COLUMN FIRST_SCN HEADING 'First SCN' FORMAT 99999999999
COLUMN NEXT_SCN HEADING 'Next SCN' FORMAT 99999999999
COLUMN PURGEABLE HEADING 'Purgeable?' FORMAT A10
 
SELECT r.CONSUMER_NAME,
       r.NAME, 
       r.FIRST_SCN,
       r.NEXT_SCN,
       r.PURGEABLE 
  FROM DBA_REGISTERED_ARCHIVED_LOG r, DBA_CAPTURE c
  WHERE r.CONSUMER_NAME = c.CAPTURE_NAME;

Your output looks similar to the following:

Capture
Process         Archived Redo Log
Name            File Name                    First SCN     Next SCN Purgeable?
--------------- ------------------------- ------------ ------------ ----------
CAPTURE_SIMP    /private1/ARCHIVE_LOGS/1_       509686       549100 YES
                3_502628294.dbf
 
CAPTURE_SIMP    /private1/ARCHIVE_LOGS/1_       549100       587296 YES
                4_502628294.dbf
 
CAPTURE_SIMP    /private1/ARCHIVE_LOGS/1_       587296       623107 NO
                5_502628294.dbf

The redo log files with YES for Purgeable? for all capture processes will never be needed by any capture process at the local database. These redo log files can be removed without affecting any existing capture process at the local database. The redo log files with NO for Purgeable? for one or more capture processes must be retained.

See Also:

"ARCHIVELOG Mode and a Capture Process"

Displaying the Last Archived Redo Entry Available to Each Capture Process

For a local capture process, the last archived redo entry available is the last entry from the online redo log flushed to an archived log file. For a downstream capture process, the last archived redo entry available is the redo entry with the most recent SCN in the last archived log file added to the LogMiner session used by the capture process.

You can display the following information about the last redo entry that was made available to each capture process by running the query in this section:

The name of the capture process
The identification number of the LogMiner session used by the capture process
The SCN of the last redo entry available for the capture process
The time when the last redo entry became available for the capture process

The information displayed by this query is valid only for an enabled capture process.

Run the following query to display this information for each capture process:

COLUMN CAPTURE_NAME HEADING 'Capture|Name' FORMAT A20
COLUMN LOGMINER_ID HEADING 'LogMiner ID' FORMAT 9999
COLUMN AVAILABLE_MESSAGE_NUMBER HEADING 'Last Redo SCN' FORMAT 9999999999
COLUMN AVAILABLE_MESSAGE_CREATE_TIME HEADING 'Time of|Last Redo SCN'

SELECT CAPTURE_NAME,
       LOGMINER_ID,
       AVAILABLE_MESSAGE_NUMBER,
       TO_CHAR(AVAILABLE_MESSAGE_CREATE_TIME, 'HH24:MI:SS MM/DD/YY') 
         AVAILABLE_MESSAGE_CREATE_TIME
  FROM V$STREAMS_CAPTURE;

Your output looks similar to the following:

Capture                                        Time of
Name                 LogMiner ID Last Redo SCN Last Redo SCN
-------------------- ----------- ------------- -----------------
STREAMS_CAPTURE                1        322953 11:33:20 10/16/03

Listing the Parameter Settings for Each Capture Process

The following query displays the current setting for each capture process parameter for each capture process in a database:

COLUMN CAPTURE_NAME HEADING 'Capture|Process|Name' FORMAT A25
COLUMN PARAMETER HEADING 'Parameter' FORMAT A25
COLUMN VALUE HEADING 'Value' FORMAT A10
COLUMN SET_BY_USER HEADING 'Set by User?' FORMAT A15

SELECT CAPTURE_NAME,
       PARAMETER, 
       VALUE,
       SET_BY_USER  
  FROM DBA_CAPTURE_PARAMETERS;

Your output looks similar to the following:

Capture
Process
Name                      Parameter                 Value      Set by User?
------------------------- ------------------------- ---------- ---------------
CAPTURE                   DISABLE_ON_LIMIT          N          NO
CAPTURE                   DOWNSTREAM_REAL_TIME_MINE Y          NO
CAPTURE                   MAXIMUM_SCN               INFINITE   NO
CAPTURE                   MESSAGE_LIMIT             INFINITE   NO
CAPTURE                   PARALLELISM               3          YES
CAPTURE                   STARTUP_SECONDS           0          NO
CAPTURE                   TIME_LIMIT                INFINITE   NO
CAPTURE                   TRACE_LEVEL               0          NO
CAPTURE                   WRITE_ALERT_LOG           Y          NO

Note:

If the Set by User? column is NO for a parameter, then the parameter is set to its default value. If the Set by User? column is YES for a parameter, then the parameter might or might not be set to its default value.

See Also:

Viewing the Extra Attributes Captured by Each Capture Process

You can use the INCLUDE_EXTRA_ATTRIBUTE procedure in the DBMS_CAPTURE_ADM package to instruct a capture process to capture one or more extra attributes from the redo log. The following query displays the extra attributes included in the LCRs captured by each capture process in the local database:

COLUMN CAPTURE_NAME HEADING 'Capture Process' FORMAT A20
COLUMN ATTRIBUTE_NAME HEADING 'Attribute Name' FORMAT A15
COLUMN INCLUDE HEADING 'Include Attribute in LCRs?' FORMAT A30

SELECT CAPTURE_NAME, ATTRIBUTE_NAME, INCLUDE 
  FROM DBA_CAPTURE_EXTRA_ATTRIBUTES
  ORDER BY CAPTURE_NAME;

Your output looks similar to the following:

Capture Process      Attribute Name  Include Attribute in LCRs?
-------------------- --------------- ------------------------------
STREAMS_CAPTURE      ROW_ID          NO
STREAMS_CAPTURE      SERIAL#         NO
STREAMS_CAPTURE      SESSION#        NO
STREAMS_CAPTURE      THREAD#         NO
STREAMS_CAPTURE      TX_NAME         YES
STREAMS_CAPTURE      USERNAME        NO

Based on this output, the capture process named streams_capture includes the transaction name (tx_name) in the LCRs that it captures, but this capture process does not include any other extra attributes in the LCRs that it captures.

See Also:

"Extra Information in LCRs"
"Managing Extra Attributes in Captured Messages"
Oracle Database PL/SQL Packages and Types Reference for more information about the INCLUDE_EXTRA_ATTRIBUTE procedure

Determining the Applied SCN for All Capture Processes in a Database

The applied system change number (SCN) for a capture process is the SCN of the most recent message dequeued by the relevant apply processes. All changes below this applied SCN have been dequeued by all apply processes that apply changes captured by the capture process.

To display the applied SCN for all of the capture processes in a database, run the following query:

COLUMN CAPTURE_NAME HEADING 'Capture Process Name' FORMAT A30
COLUMN APPLIED_SCN HEADING 'Applied SCN' FORMAT 99999999999

SELECT CAPTURE_NAME, APPLIED_SCN FROM DBA_CAPTURE;

Your output looks similar to the following:

Capture Process Name           Applied SCN
------------------------------ -----------
CAPTURE_EMP                         177154

Determining Redo Log Scanning Latency for Each Capture Process

You can find the following information about each capture process by running the query in this section:

The redo log scanning latency, which specifies the number of seconds between the creation time of the most recent redo log entry scanned by a capture process and the current time. This number might be relatively large immediately after you start a capture process.
The seconds since last recorded status, which is the number of seconds since a capture process last recorded its status.
The current capture process time, which is the latest time when the capture process recorded its status.
The message creation time, which is the time when the data manipulation language (DML) or data definition language (DDL) change generated the redo data for the most recently captured message.

The information displayed by this query is valid only for an enabled capture process.

Run the following query to determine the redo scanning latency for each capture process:

COLUMN CAPTURE_NAME HEADING 'Capture|Process|Name' FORMAT A10
COLUMN LATENCY_SECONDS HEADING 'Latency|in|Seconds' FORMAT 999999
COLUMN LAST_STATUS HEADING 'Seconds Since|Last Status' FORMAT 999999
COLUMN CAPTURE_TIME HEADING 'Current|Process|Time'
COLUMN CREATE_TIME HEADING 'Message|Creation Time' FORMAT 999999

SELECT CAPTURE_NAME,
       ((SYSDATE - CAPTURE_MESSAGE_CREATE_TIME)*86400) LATENCY_SECONDS,
       ((SYSDATE - CAPTURE_TIME)*86400) LAST_STATUS,
       TO_CHAR(CAPTURE_TIME, 'HH24:MI:SS MM/DD/YY') CAPTURE_TIME,       
       TO_CHAR(CAPTURE_MESSAGE_CREATE_TIME, 'HH24:MI:SS MM/DD/YY') CREATE_TIME
  FROM V$STREAMS_CAPTURE;

Your output looks similar to the following:

Capture    Latency               Current
Process         in Seconds Since Process           Message
Name       Seconds   Last Status Time              Creation Time
---------- ------- ------------- ----------------- -----------------
CAPTURE          4             4 12:04:13 03/01/02 12:04:13 03/01/02

The "Latency in Seconds" returned by this query is the difference between the current time (SYSDATE) and the "Message Creation Time." The "Seconds Since Last Status" returned by this query is the difference between the current time (SYSDATE) and the "Current Process Time."

Determining Message Enqueuing Latency for Each Capture Process

You can find the following information about each capture process by running the query in this section:

The message enqueuing latency, which specifies the number of seconds between when an entry was recorded in the redo log and when the message was enqueued by the capture process
The message creation time, which is the time when the data manipulation language (DML) or data definition language (DDL) change generated the redo data for the most recently enqueued message
The enqueue time, which is when the capture process enqueued the message into its queue
The message number of the enqueued message

The information displayed by this query is valid only for an enabled capture process.

Run the following query to determine the message capturing latency for each capture process:

COLUMN CAPTURE_NAME HEADING 'Capture|Process|Name' FORMAT A10
COLUMN LATENCY_SECONDS HEADING 'Latency|in|Seconds' FORMAT 999999
COLUMN CREATE_TIME HEADING 'Message Creation|Time' FORMAT A20
COLUMN ENQUEUE_TIME HEADING 'Enqueue Time' FORMAT A20
COLUMN ENQUEUE_MESSAGE_NUMBER HEADING 'Message|Number' FORMAT 999999

SELECT CAPTURE_NAME,
       (ENQUEUE_TIME-ENQUEUE_MESSAGE_CREATE_TIME)*86400 LATENCY_SECONDS, 
       TO_CHAR(ENQUEUE_MESSAGE_CREATE_TIME, 'HH24:MI:SS MM/DD/YY') CREATE_TIME,
       TO_CHAR(ENQUEUE_TIME, 'HH24:MI:SS MM/DD/YY') ENQUEUE_TIME,
       ENQUEUE_MESSAGE_NUMBER
  FROM V$STREAMS_CAPTURE;

Your output looks similar to the following:

Capture    Latency
Process         in Message Creation                            Message
Name       Seconds Time                 Enqueue Time          Number
---------- ------- -------------------- -------------------- -------
CAPTURE          0 10:56:51 03/01/02    10:56:51 03/01/02     253962

The "Latency in Seconds" returned by this query is the difference between the "Enqueue Time" and the "Message Creation Time."

Displaying Information About Rule Evaluations for Each Capture Process

You can display the following information about rule evaluation for each capture process by running the query in this section:

The name of the capture process.
The number of changes discarded during prefiltering since the capture process was last started. The capture process determined that these changes definitely did not satisfy the capture process rule sets during prefiltering.
The number of changes kept during prefiltering since the capture process was last started. The capture process determined that these changes definitely satisfied the capture process rule sets during prefiltering. Such changes are converted into LCRs and enqueued into the capture process queue.
The total number of prefilter evaluations since the capture process was last started.
The number of undecided changes after prefiltering since the capture process was last started. These changes might or might not satisfy the capture process rule sets. Some of these changes might be filtered out after prefiltering without requiring full evaluation. Other changes require full evaluation to determine whether they satisfy the capture process rule sets.
The number of full evaluations since the capture process was last started. Full evaluations can be expensive. Therefore, capture process performance is best when this number is relatively low.

The information displayed by this query is valid only for an enabled capture process.

Run the following query to display this information for each capture process:

COLUMN CAPTURE_NAME HEADING 'Capture|Name' FORMAT A15
COLUMN TOTAL_PREFILTER_DISCARDED HEADING 'Prefilter|Changes|Discarded' 
  FORMAT 9999999999
COLUMN TOTAL_PREFILTER_KEPT HEADING 'Prefilter|Changes|Kept' FORMAT 9999999999
COLUMN TOTAL_PREFILTER_EVALUATIONS HEADING 'Prefilter|Evaluations' 
  FORMAT 9999999999
COLUMN UNDECIDED HEADING 'Undecided|After|Prefilter' FORMAT 9999999999
COLUMN TOTAL_FULL_EVALUATIONS HEADING 'Full|Evaluations' FORMAT 9999999999

SELECT CAPTURE_NAME,
       TOTAL_PREFILTER_DISCARDED,
       TOTAL_PREFILTER_KEPT,
       TOTAL_PREFILTER_EVALUATIONS,
       (TOTAL_PREFILTER_EVALUATIONS - 
         (TOTAL_PREFILTER_KEPT + TOTAL_PREFILTER_DISCARDED)) UNDECIDED,
       TOTAL_FULL_EVALUATIONS
  FROM V$STREAMS_CAPTURE;

Your output looks similar to the following:

Capture     Prefilter   Prefilter               Undecided
Process       Changes     Changes   Prefilter       After        Full
Name        Discarded        Kept Evaluations   Prefilter Evaluations
---------- ---------- ----------- ----------- ----------- -----------
STM1$CAP       219493           2      219961         466           0

The total number of prefilter evaluations equals the sum of the prefilter changes discarded, the prefilter changes kept, and the undecided changes.

See Also:

"Capture Process Rule Evaluation"