Valid for

Extract

Description

Use SOURCEISFILE or SOURCEISTABLE to specify whether the source is a file or a table. In many cases, source and target files are synchronized with utilities such as FUP DUP or SQLCI LOAD. These utilities establish a point at which subsequent changes made to the source can be applied accurately at the target. However, if mapping is specified between source and target, or if the target is a non-NonStop database, conversion must take place before load.

SOURCEISFILE reads and processes records from the source file itself rather than the audit trail. If you specified user exits or column maps when Extract processes database changes through the audit trail, also specify SOURCEISFILE so that the same mapping can be applied before a full-scale file load. Therefore, only one set of mapping routines is required for managing both full synchronization and incremental change activities.

Syntax

SOURCEISFILE | SOURCEISTABLE
[, FASTUNLOAD | FASTUNLOADSHARED]
[, SQLPREDICATE] 
[, SELECTVIEW] 
[, RESTARTCHECKPOINTS]

FASTUNLOAD

Processes the file or table several times faster than the default method. Records are output in random order, rather than primary key order. FASTUNLOAD has no effect when an SQL view is specified. The FILE parameter option PARTITIONS can restrict the data retrieved to a certain subset of the file or table.

FASTUNLOAD fails if other openers exist for the file or table (the file is opened in protected mode).

FASTUNLOADSHARED

Allows a shared open of the source file or table. Use this only on files that are not receiving updates at the same time data is being extracted.

SQLPREDICATE

Uses any WHERE clause designated as part of a TABLE entry as criteria when selecting data from the source table. SQLPREDICATE can dramatically reduce extraction time when only part of the source table needs to be extracted. This option only works when the source is an SQL table.

You can start separate Extract processes to retrieve data from selected partitions from large tables in parallel. Each process selects a range of data from one or more partitions. When SQLPREDICATE is specified, only relevant partitions are scanned.

SELECTVIEW

Selects data from a specified SQL view in the FILE parameter. Without SELECTVIEW, Extract selects data from the base table of the view, then maps the base table columns to the view columns (this also occurs when processing audit trails and a view is specified).

SELECTVIEW is required to process multiple table joins and aggregation views. Use SELECTVIEW to format complex query output for compatibility with other platforms. Rather than using standard utilities that output a record at a time, this method takes advantage of Extract's high performance buffering and cross-platform features.

RESTARTCHECKPOINTS

Instructs Extract to save checkpoint information allowing restart at the last record read if the process stops or abends. See"Using RESTARTCHECKPOINTS" for conditions and restrictions.

Using RESTARTCHECKPOINTS

You can use RESTARTCHECKPOINTS for:

• SQL/MP source tables with or without the SQLPREDICATE option

• Enscribe whether or not you use the FILE STARTKEY and ENDKEY options

• Both SQL/MP and Enscribe with or without FASTUNLOAD.

RESTARTCHECKPOINTS is valid only for Extracts added from GGSCI using SOURCEISFILE or SOURCEISTABLE.

A positioned restart is valid only if RESTARTCHECKPOINTS is in the parameter file when the Extract starts initially. The process will start from the beginning of the file if RESTARTCHECKPOINTS is added or removed for any subsequent restart.

Either SOURCEDEFS or DICTIONARY and DEF are required for Enscribe source files.

You must not make any of the following changes to the parameter file when restarting from a position other than the beginning of the file. If you must make these changes, you must delete and re-add the Extract group.

• Removing checkpoint information by:

  • Removing the current Data File Checkpoint file from the parameter file. This file can be identified with the INFO EXTRACT command.

    GGSCI> INFO EXTRACT EXTPART
    
    Extract  EXTPART      Last Started 2010-12-06 12:39  Status RUNNING
    Task type             SourceIsFile
    Process  $TSE01       Checkpoint Lag: unknown
    Data File Checkpoint  \NY.$DATA02.ACDATA.ACPART
    .
    .
    .
    

  • Removing the current output checkpoint. This is also identified in the INFO EXTRACT command.

    GGSCI> INFO EXTRACT EXTPART
    .
    .
    .
                                         Record       30977
    Target Extract Trails                                        Rba     Max MB
      \NY.$DATA02.ACDATA.TX000001                              2168775      3.
    

• Adding or removing the FASTUNLOAD option

• Adding a new EXTFILE, RMTFILE, or RMTTASK

• Changing the source file or table significantly, such as changing the key columns or their length or datatype

• Changing a STARTKEY or ENDKEY in a way that alters the file access method.

It is not recommended that you add files or tables to the parameter file after start-up and before a restart. They may not be extracted.

Replicat processes require the HANDLECOLLISIONS parameter during a restart of a RMTTASK Extract.