CDC Guide for i5/OS

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Explicit Override Statements

Use explicit override statements to specify an extraction restart point for a specific source in a CDC session. You can specify multiple explicit override statements, each for a different source.

When you warm start a CDC session, the explicit override statement for a source object overrides the restart tokens in the state table or state file for that source. You can use explicit override statements in conjunction with special override statements to provide override restart tokens for all sources in a CDC session.

An explicit override statement for a source can specify either a pair to restart tokens that define a specific point in the change stream or the CURRENT_RESTART option for the current end of the change stream. Alternatively, if you use the PowerExchange Logger for Linux, UNIX, and Windows with a CDC application connection, you can optionally define an explicit override statement that specifies a time-based restart point for extraction processing in the Logger log files.

To specify restart tokens for a source, enter a pair of statements, each containing the extraction map name and a sequence token (restart1) or restart token (restart2) value. Use the following syntax:

extractionMapName=restart1_token
extractionMapName=restart2_token

Because a source can have multiple extraction maps with distinct names, you might need to define multiple pairs of explicit override statements for a source.

For z/OS sources, if you use the default value of Y for the FUZZYRSTART parameter in the LRAP CAPI_CONNECTION statement, you can enter a restart2 position other than a begin-uow position from which to start extraction processing in the PowerExchange Logger for z/OS logs. In the following example, the restart2_token value points to a RBA position that does not coincide with a begin-uow record and the restart1_token value points to a position before the restart2_token position:

For the restart1_token value, specify

000000000001000000000000000000000000000000000000

. This value consists of 48 zeroes with a "1" in the twelfth position. With this value, the restart2_token value will determine the records to be returned by the extraction.

For the restart2_token value, specify a value that consists of a 6-byte Logger ID in EBCDIC format (padded with spaces) + a 6-byte RBA position + 8 zeroes. The RBA position can be any RBA in the logs near where you want to restart extraction processing. For example:

E2C2F2D340400000000AEF4000000000

With these restart token settings, PowerExchange begins extraction processing at the first record that is at or past the restart1_token position and in the first UOW that is returned based on the restart2_token position.

To specify the current end of the change stream as the restart point, use the following syntax:

extractionMapName=CURRENT_RESTART

To specify a time-based restart point in the PowerExchange Logger logged data, enter a pair of statements, one containing the RESTART_TIME option and the other containing a date and time value. Use the following syntax:

extractionMapName=RESTART_TIME
extractionMapName=datetime

Parameter descriptions:

extractionMapName: The name of an extraction map for the data source. To determine the extraction map name, use one of the following methods:

For CDC data map sources, see the
Schema Name Override
and
Map Name Override
attributes in the session properties. These attributes override the schema name and map name in the source extraction map. Or, in Designer, see the
Schema Name
and
Map Name
values in the source Metadata Extensions.

For relational sources, see the
Extraction Map Name
attribute in the session properties.

After the extraction map has been used to extract change data, the table name is appended to this value in the format extractionMapName_tableName. Use the full name when defining an explicit override statement.
restart1_token: The sequence token portion of a restart token pair. This value varies based on data source type.
restart2_token: The restart token portion of a restart token pair. This value based on data source type.
CURRENT_RESTART: The option that generates a pair of restart tokens that mark the current end of the change stream. The PWXPC CDC reader opens a separate connection to PowerExchange, requests the generation of current restart tokens, and then provides the token values to the applicable source.

Optionally, you can generate current restart tokens in the
Database Row Test
dialog box of the PowerExchange Navigator.

Use the CURRENT_RESTART option only for CDC sessions that use real-time extraction mode or continuous extraction mode.
RESTART_TIME: If you use the PowerExchange Logger for Linux, UNIX, and Windows log files, this option allows you to specify a date and time value as the restart point for extraction processing in the Logger log files.
datetime: The date and time to use as the restart point in PowerExchange Logger for Linux, UNIX, and Windows log files. This value must be in the format YYYYMMDDhhmmssuuuuuu, where YYYY is a four-digit year, MM is the month, DD is the day of the month, hh is hours, mm is minutes, ss is seconds. and uuuuuu is microseconds.

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CDC Guide for i5/OS

CDC Guide for i5/OS

Explicit Override Statements

Explicit Override Statements