SAP HANA Developer Guide - Get a Free Blog

5.1 Schema
Relational databases contain a catalog that describes the various elements in the system. The catalog divides the
database into sub-databases known as schema. A database schema enables you to logically group together
objects such as tables, views, and stored procedures. Without a defined schema, you cannot write to the catalog.
SAP HANA Extended Application Services (SAP HANA XS) enables you to create a database schema as a
transportable design-time file in the repository. Repository files can be read by applications that you develop.
If your application refers to the repository (design-time) version of a schema rather than the runtime version in
the catalog, for example, by using the explicit path to the repository file (with suffix), any changes to the
repository version of the file are visible as soon as they are committed to the repository. There is no need to wait
for the repository to activate a runtime version of the schema.
If you want to define a transportable schema using the design-time hdbschema specifications, use the
configuration schema illustrated in the following example:
string schema_name
The following example shows the contents of a valid transportable schema-definition file for a schema called
MYSCHEMA:
schema_name=”MYSCHEMA”;
The schema is stored in the repository with the schema name MYSCHEMA as the file name and the
suffix .hdbschema, for example, MYSCHEMA.hdbschema.
Schema Activation
If you want to create a schema definition as a design-time object, you must create the schema as a flat file. You
save the file containing the schema definition with the suffix .hdbschema in the appropriate package for your
application in the SAP HANA repository. You can activate the design-time objects at any point in time.
Note: On activation of a repository file, the file suffix, for example, .hdbschema, is used to determine
which runtime plugin to call during the activation process. The plug-in reads the repository file selected for
activation, parses the object descriptions in the file, and creates the appropriate runtime objects.
If you activate a schema-definition object in SAP HANA, the activation process checks if a schema with the same
name already exists in the SAP HANA repository. If a schema with the specified name does not exist, the
repository creates a schema with the specified name and makes _SYS_REPO the owner of the new schema.
Note: The schema cannot be dropped even if the deletion of a schema object is activated.
If you define a schema in SAP HANA XS, note the following important points regarding the schema name:
● Name mapping
The schema name must be identical to the name of the corresponding repository object.
● Naming conventions
SAP HANA Developer Guide
Setting Up the Persistence Model
P U B L I C
© 2012 SAP AG. All rights reserved. 75