Landing in a data lake settings

You can change the default data lake landing settings according to your needs.

General

Update method

You can land data in two different modes. It is not possible to change mode once the data lake landing task is prepared.

• Change data capture (CDC): The data lake landing tasks starts with a full load (during which all of the selected tables are landed). The landed data is then kept up-to-date using CDC (Change Data Capture) technology.

  Information noteCDC (Change Data Capture) of DDL operations is not supported.
• Reload: Performs a full load of the data from the selected source tables to the target platform and creates the target tables if necessary. The full load occurs automatically when the task is started, but can also be performed manually or scheduled to occur periodically as needed.

Folder to use

Select one of the following, according to which bucket folder you want the files to be written to:

• Default folder: The default folder format is <your-project-name>/<your-task-name>
• Root folder: The files will be written to the bucket directly.

• Folder: Enter the folder name. The folder will be created during the data lake landing task if it does not exist.

  Information note The folder name cannot include special characters (for example, @, #, !, and so on).

Change data partitioning

In a standard landing task, changes are landed to the target in no particular order. Change Data Partitioning enables processing of Change Data from many tables in a consistent fashion. You can define the duration of partitions as well as the partitioning base time, thereby ensuring overall consistency of the partitioned data (i.e. no partial transactions, no order headers without order rows, and so on.)

Information about the partitions is recorded in the attrep_cdc_partitions Control Table in the target database. This information can be used to identify partitioned data that needs to be further processed.

The partitioning options are as follows:

• Partition every - Specify the length (in hours and minutes) of each partition.

  Information note

  It is recommended to specify a partition length in excess of one hour. Although specifying a partition length less than one hour may improve latency, creating many partitions on the target may also impact (target) performance (especially in systems with large volumes of changes).

  If you resume a task from BEFORE the time that the last partition was created, the data lake landing task will write to a partition that has already been closed.

• Partition base time - Partitions are created during a 24 hour time period, which is calculated according to the specified “Partitioning base time” on the source database (in UTC time). For example, a partition interval of 8 hours with a “Partitioning base time” time of 02:00 will create the following partitions: 02:00-10:00, 10:00-18:00, 18:00-02:00 - but not necessarily in that order. For instance, if a task started at 01:00, then the timeframe of the first partition will be 18:00-02:00. Additionally, if a task started in the middle of a partition (e.g. at 04:00), its Change Data will be inserted into the 02:00-10:00 partition (even though no changes were captured before 04:00).

Data uploading

File attributes

Field delimiter

The delimiter that will be used to separate fields (columns) in the target files. The default is a comma.

Example using a comma as a delimiter:

"mike","male"

Delimiters can be standard characters or a hexadecimal (hex) value. Note that the "0x" prefix must be used to denote a hexadecimal delimiter (e.g. 0x01 = SOH). In the Field delimiter, Record delimiter and Null value fields, the delimiter can consist of concatenated hex values (e.g. 0x0102 = SOHSTX), whereas in the Quote character and Quote escape character fields, it can only be a single hex value.

The hexadecimal number 0x00 is not supported (i.e. only 0x01-0xFF are supported).

Null value

The string that will be used to indicate a null value in the target files.

Example (where \n is the record delimiter and @ is the null value):

Record delimiter

The delimiter that will be used to separate records (rows) in the target files. The default is a newline (\n).

Example:

Quote character

The character that will be used at the beginning and end of a text column. The default is the double-quote character ("). When a column that contains column delimiters is enclosed in double-quotes, the column delimiter characters are interpreted as actual data, and not as column delimiters.

Example (where a @ is the quote character):

Quote escape character

The character used to escape a quote character in the actual data. The default is the double-quote character (").

Example (where " is the quote character and \ is the escape character):

Parquet version

Select which version to use according to which version the target platform supports. Note that Parquet version 1.0 supports the MICRO timestamp unit only, while Parquet version 2.6 supports both MICRO and NANO timestamp units.

Parquet timestamp unit

When Parquet version is set to 2.6, choose MICRO or NANO. When Parquet version is set to 1.0, only MICRO is supported.

Parquet maximum LOB size (KB)

The default maximum LOB size is 64 KB and the maximum value you can enter in this field is 10,000 KB. Handling LOB columns requires greater resources, which in turn impacts performance. Only increase this value is you are replicating LOB data larger than 64 KB and you require all the LOB data to be replicated to the target.

Maximum file size

The maximum size a file can reach before it is closed (and optionally compressed).

The maximum size a file can reach before it is closed. Smaller files might be uploaded faster (depending on the network) and improve performance when used in conjunction with the parallel execution option. However, it is generally considered bad practice to clutter the database with small files.

Compress files using

Choose one of the compression options to compress the target files or NONE (the default) to leave them uncompressed. Note that the available compressions options are determined by the selected file format.

Add metadata header

You can optionally add a header row to the data files. The header row can contain the source column names and/or the intermediate (i.e. Data Movement gateway) data types.

Example of a target file with a header row when both With column names and With data types are selected:

Position:DECIMAL(38,0),Color:VARCHAR(10)

1,"BLUE"

2,"BROWN"

3,"RED"

...

Change processing

This section describes conditional settings in Change Processing.

Apply/store changes when

• File size reaches: Specify the maximum size of Change Data to accumulate before uploading the file to the target.
• Elapsed time reaches: Elapsed time reaches x.

Metadata files

When the Create metadata files in the target folder option is selected, for each data file, a matching metadata file with a .dfm extension will be created under the specified target folder. The metadata files provide additional information about the task/data such as the source connector type, the source table name, the number of records in the data file, and so on.

For a full description of the metadata file as well as possible uses, see Metadata file description

Metadata

LOB columns

• Include LOB columns and limit column size to (KB):

  You can choose to include LOB columns in the task, and set the maximum LOB size. LOBs that are larger than the maximum size will be truncated.

Control tables

Select which of the following Control tables you want to be created on the target platform:

• Landing Status: Provides details about the current landing task including task status, amount of memory consumed by the task, number of changes not yet applied to the data platform and the position in the source endpoint from which Data Movement gateway is currently reading.
• Suspended Tables: Provides a list of suspended tables, and the reason they were suspended.
• Landing History: Provides information about the task history including the number and volume of records processed during a landing task, latency at the end of a CDC task, and more.
• Change Data Partitions: Provides records of partitions created on the target database due to Change data partitioning. You can use this information to identify partitioned data that needs to be further processed.

For a detailed description of each of the Control Tables, see Control Tables

Full load

Performance tuning

• Maximum number of tables to load in parallel: Enter the maximum number of tables to load into the target at one time. The default value is 5.

• Transaction consistency timeout (seconds): Enter the number of seconds to wait for open transactions to close, before beginning the Full Load operation. The default value is 600 (10 minutes). The full load will start after the timeout value is reached even if there are transactions that are still open.

  Information noteTo replicate transactions that were open when Full Load started but were only committed after the timeout value was reached, you need to reload the target tables.
• Commit rate during full load: The maximum number of events that can be transferred together. The default value is 10000.

After full load completes

Create primary key or unique: Select this option if you want to delay creation of the primary key or unique index on the data platform until after full load completes.

For initial load

When moving data from a SaaS application source, you can set how to perform the initial full load:

Error handling

Data errors

Data truncation errors

For data truncation errors: Select what you want to happen when a truncation occurs in one or more specific records. You can select one of the following from the list:

• Ignore: The task continues and the error is ignored.
• Suspend table: The task continues, but data from the table with the error record is moved into an error state and its data is not replicated
• Stop task: The task is stopped and manual intervention is required.

Other data errors

For other data errors: Select what you want to happen when an error occurs in one or more specific records. You can select one of the following from the list:

• Ignore: The task continues and the error is ignored.
• Suspend table: The task continues, but data from the table with the error record is moved into an error state and its data is not replicated
• Stop task: The task is stopped and manual intervention is required.

Escalating data error handling

Escalate error handling when other data errors reach (per table): Select this check box to escalate error handling when the number of non-truncation data errors (per table) reaches the specified amount. Valid values are 1-10,000.

Escalation action: Choose what should happen when error handling is escalated. Note that the available actions are dependent on the action selected from the For other data errors drop-down list described above.

• Suspend table (default): The task continues, but data from the table with the error record is moved into an error state and its data is not landed.

• Stop task: The task is stopped and manual intervention is required.

Table errors

When encountering a table error: Select one of the following from the drop-down list:

• Suspend table (default): The task continues but data from the table with the error record is moved into an error state and its data is not replicated
• Stop task: The task is stopped and manual intervention is required.

Escalate error handling when table errors reach (per table): Select this check box to escalate error handling when the number of table errors (per table) reaches the specified amount. Valid values are 1-10,000.

Escalation action: The escalation policy for table errors is set to Stop task and cannot be changed.

Environmental

• Maximum retry count: Select this option and then specify the maximum number of attempts to retry a task when a recoverable environmental error occurs. After the task has been retried the specified number of times, the task is stopped and manual intervention is required.

  To never retry a task, clear the check box or specify "0".

  To retry a task an infinite number of times, specify "-1"

  • Interval between retry attempts (seconds): Use the counter to select or type the number of seconds that the system waits between attempts to retry a task.

    Valid values are 0-2,000.

• Increase retry interval for long outages: Select this check box to increase the retry interval for long outages. When this option is enabled, the interval between each retry attempt is doubled, until the Maximum retry interval is reached (and continues retrying according to the specified maximum interval).
  • Maximum retry interval (seconds): Use the counter to select or type the number of seconds to wait between attempts to retry a task when the Increase retry interval for long outages option is enabled. Valid values are 0-2,000.

Change processing tuning

Transactional offload tuning

• Offload transactions in progress to disk if:

  Transaction data is usually kept in memory until it is fully committed to the source or target. However, transactions that are larger than the allocated memory or that are not committed within the specified time limit will be offloaded to disk.

  • Total memory size for all transactions exceeds (MB): The maximum size that all transactions can occupy in memory before being offloaded to disk. The default value is 1024.
  • Transaction duration exceeds (seconds): The maximum time that each transaction can stay in memory before being offloaded to disk. The duration is calculated from the time Data Movement gateway started capturing the transaction. The default value is 60.

Batch tuning

• Minimum number of changes per transaction: The minimum number of changes to include in each transaction. The default value is 1000.

  Information note

  The changes will be applied to the target either when the number of changes is equal to or greater than the Minimum number of changes per transaction value OR when the Maximum time to batch transactions before applying (seconds) value described below is reached - whichever occurs first. Because the frequency of changes applied to the target is controlled by these two parameters, changes to the source records may not immediately be reflected in the target records.

• Maximum time to batch transactions before applying (seconds): The maximum time to collect transactions in batches before declaring a timeout. The default value is 1.

Interval

Read changes every (Minutes)

Set the interval between reading changes from the source in minutes. The valid range is 1 to 1,440.

Miscellaneous tuning

• Statements cache size (number of statements): The maximum number of prepared statements to store on the server for later execution (when applying changes to the target). The default is 50. The maximum is 200.

• DELETE and INSERT when updating a primary key column: This option requires full supplemental logging to be turned on in the source database.

Character substitution

You can substitute or delete source characters in the target database and/or you can substitute or delete source characters that are not supported by a selected character set.

Substituting or deleting source characters

Use the Substitute or delete source characters table to define replacements for specific source characters. This may be useful, for example, when the Unicode representation of a character is different on the source and target platforms. For example, on Linux, the minus character in the Shift_JIS character set is represented as U+2212, but on Windows it is represented as U+FF0D.

Substituting or deleting source characters unsupported by the selected character set

Use the Unsupported source characters by character set table to define a single replacement character for all characters not supported by the selected character set.

More options

These options are not exposed in the UI as they are only relevant to specific versions or environments. Consequently, do not set these options unless explicitly instructed to do so by Qlik Support or product documentation.

To set an option, simply copy the option into the Add feature name field and click Add. Then set the value or enable the option according to the instructions you received.