what is the use of deployment code in hybris?

<itemtype code="IntegrationSystemCredentials" autocreate="true" generate="true">
                <deployment **table**="IntegrationSystemCredentials" typecode="11000" />
</itemtype>

In the above code i have mentioned deployment table and typecode. why we are using both?

> In the above code i have mentioned deployment table and typecode. why
> we are using both?

The short answer is: It's because they serve different purposes.

deployment table

Using deployment table, you map a database table to the itemtype. If you do not mention deployment table, the values of the attributes of the itemtype will be saved into the deployment table of its parent itemtype; in other words, in absence of the deployment table in the itemtype definition, the database table of the patent itemtype will be mapped with the itemtype.

If you are creating an itemtype by extending GenericItem, you must declare a deployment table (a mechanism to avoid the attributes of the itemtype getting saved in GenericItem table). However, if you are extending some other itemtype e.g. Product, you should avoid declaring deployment table as much as possible in order to avoid too many joins required during the execution of the Flexible Search Query.

Note that GenericItem is the default parent of an itemtype i.e. if you do not declare extends... in the itemtype definition, the itemtype will, by default, extend GenericItem e.g. the following itemtype definition will fail compilation because DummyItem extends GenericItem by default but there is no deployment table mentioned for it.

<items xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:noNamespaceSchemaLocation="items.xsd">
	<itemtypes>
		<itemtype code="DummyItem" autocreate="true">
			<attributes>
				<attribute qualifier="uname" type="java.lang.String">
					<modifiers read="true" write="true" search="true" initial="true" optional="false"/>
					<defaultvalue>"Hello"</defaultvalue>
					<persistence type="property"></persistence>
				</attribute>
			</attributes>
		</itemtype>
	</itemtypes>
</items>

typecode

The typecode attribute is a unique number to reference the type. The value of the typecode attribute must be a positive integer between 0 and 32767 (2^15-1) and must be unique throughout your hybris application as it is part of the PK generation mechanism as shown below:

private static PK createPK_Counter(int typecode, long counter) {
	if (typecode >= 0 && typecode <= 32767) {
		//...
	} else {
		throw new IllegalArgumentException("illegal typecode : " + typecode + ", allowed range: 0-" + 32767);
	}
}

Check this and this to learn more about it.

> what is the deployment table in hybris?

Items within SAP Commerce are made persistent by writing values into a database. Within the database, the values are stored in tables. SAP Commerce allows you to explicitly define the database tables where the values of instances of a given type will be written. This can be done by defining the deployment tag.
Like.
<deployment table="mytype_deployment" typecode="12345" />

> When to define the deployment table?

One should define the deployment table for an item type when

• Your item type doesn't extend any other item type (except GenericItem, which is by default)

• Your item type extend existing item type for which there is no deployment table defined

Read more Specifying a Deployment for Platform Types