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Using the Table Lookup Service instead of adding tableCreate in each workflow instance will increase the throughput with less fewer duplicated tables, fewer lookups, and reduced memory consumption.

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The Shared Table profile is loaded when you start a workflow that depends on it. Changes to the profile become effective when you restart the workflow and each time you save the profile.

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The type of memory allocation chosen for the shared tables are is configured in the Shared Table profile by selecting a Table Storage parameter. If relevant, you can select an Index Storage parameter and also Variable Width Varchar Columns. For further information about these settings, see the section below, Shared Table Profile Configuration.

For further information about memory allocation in, see the /wiki/spaces/MD82/pages/3778529 System Administration Guide.

Shared Table Profile Configuration

The Shared Table profile configuration is opened by clicking on the New Configuration button in Desktop and selecting the Shared Table Profile option.

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The Shared Table profile dialog

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The Shared Table profile dialog contains the following configurations:

SettingDescription
Database

Database

Click the Browse...button and select the Database profile you want to use. Any type of database that has been configured in a database profile can be used. See Database Profile for further information.

Release Timeout (seconds)

If this check box is selected, the table will be released when the entered number of seconds have passed since the workflows accessing the table were stopped. The entered number of seconds must be larger than 0.

If this check box is not selected, the table will stay available until the execution context is restarted.

Refresh Interval (seconds)

Select this check box in order to refresh the data in the table with the interval entered. The entered number of seconds must be larger than 0.

If this check box is not selected, the table will only be refreshed if the APL function tableRefreshShared is used. For more information regarding the function, see the section below, tableRefreshShared.

Note
titleNote!

The interval for checking if the table needs to be refreshed is 10 seconds, which is the minimum time before a new refresh is performed.

If a refresh fails, an error is generated in system log, but the table is not cleared - the old data remains in the shared table. A new refresh is initiated every 10th second, until the refresh has finished successfully.


Table Storage
Object

Select this option to set the Table Storage to Object. If you select this option, the shared tables are stored as Java objects on the JVM heap.

Note
titleNote!

If you have selected to use a profile with the CSV database type, this is the only option available if you have not configured properties using Advanced Connection Setup.


On Heap

Select this option to set the Table Storage to On Heap. If you select this option, the shared tables are stored in a compact format on the JVM heap. If you select On Heap, you must select an option for the Index Storage.

Note
titleNote!

If you have selected to use a profile with the CSV database type, this option is only available if you have configured properties for this using Advanced Connection Setup.


Off Heap

Select this option to set the Table Storage to Off Heap. If you select this option, the shared tables are stored in a compact format outside the JVM heap.

Note
titleNote!

You are required to set the jdk parameter in the relevant Execution Context pico configuration, for example:

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$ mzsh topo set topo://container:<container>/pico:<pico>/obj:config.jvmargs \
'maxDirect:["-XX:MaxDirectMemorySize=4096M"]'



Note
titleNote!

If you have selected to use a profile with the CSV database type, this option is only available if you have configured properties for this using Advanced Connection Setup.

If you select Off Heap, you must select an option for the Index Storage.

Unsafe

Select this option to set the Table Storage to Unsafe. If you select this option, the shared tables are stored in a compact format. If you select Unsafe, you must select an option for the Index Storage.

Note
titleNote!

If you have selected to use a profile with the CSV database type, this option is only available if you have configured properties for this using Advanced Connection Setup.


Primitive Lookup

Select this option to set the Table Storage to Primitive Lookup. This provides simple lookup tables with a fast lookup function but they are limited to two columns of type Int/Long for the key (column 1) and type Short/Int/Long for the value (column 2). Lookup operations on Primitive Lookup tables are limited to the equals operation on column 1.

Note
titleNote!

If you use the  Primitive Lookup  option with a database profile that is configured for Oracle, using the Oracle column type NUMBER with a precision greater than 10 may cause errors.


Note
titleNote!

If you have selected to use a profile with the CSV database type, this option is only available if you have configured properties for this using Advanced Connection Setup.


Index Storage
Object

Select this option to set the Index Storage to Object. If you select this option, the index is stored as Java objects on the JVM heap. This option is only available if you have selected On Heap, Off Heap or Unsafe for Table Storage.

Pointer

Select this option to set the Index Storage to Pointer. If you select this option, the index is stored as pointers to the table data. This option is only available if you have selected On Heap, Off Heap or Unsafe for Table Storage.

Cached Long/Int PointerSelect this option to set the Index Storage to Cached Long/Int Pointer. This option is only available if you have selected On Heap, Off Heap or Unsafe for Table Storage. For numeric index columns, the Cached Long/Int Pointer can be used for faster lookups, but at the cost of slightly higher memory consumption.
Variable Width Varchar ColumnsSelect this check box to enable variable width storage of varchar columns. This reduces memory usage for columns that are wide and of varying width.
SQL Load Statement

SQL Load Statement

In this field, an SQL SELECT statement should be entered in order to create the contents of the table returned by the tableCreateShared APL function.

The following statement will return a table named MyTable with the columns key and value when the tableCreateShare function is used together with this profile.

Info
titleExample - SQL SELECT statement


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SELECT key,value FROM MyTable


If no data has been fetched from the database, SQL errors in the table lookup will cause runtime errors (workflow aborts). However, if data has already been fetched from the database then this data will be used. This will also be logged in the System Log.

Whenever possible, use values of the type long instead of the types date or string. This may improve performance.

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titleExample - Using SQL SELECT statement


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SELECT to_number(user_id) as USER_ID, 
 to_number(to_char(nvl(start_date,to_date(
	'19000101010101',
	'yyyymmddhh24miss')),
	'yyyymmddhh24miss')) as START_DATE,
 to_number(to_char(nvl(end_date, to_date(
	'99990101010101',
	'yyyymmddhh24miss')), 
	'yyyymmddhh24miss')) as END_DATE
 FROM MyTable



Table Indices

If you want to create an index for one or several columns of the shared table, these columns can be added in this field by clicking the Add ...button and adding the columns for which you want to create an index. The index will start with 0 for the first column.

Note
titleNote!

An index will not be created unless there are at least five rows in the table.

Create indices in the Shared Table profile based on the data that is fetched from the database. Even if you look up multiple columns in APL, using one index instead of several may result in improved performance. 

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The following functions are included for in the Table Lookup Service:

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