RDF Semantic Graph is automatically enabled when Spatial and Graph Release 12.2 or later is installed.

If RDF Semantic Graph was enabled successfully, a row with the following column values will exist in the MDSYS.RDF_PARAMETER table:

• NAMESPACE: MDSYS

• ATTRIBUTE: SEM_VERSION

• VALUE: (string starting with 12.2)

• DESCRIPTION: VALID

If you are upgrading from Oracle Database Release 11.1 or 11.2 that includes the semantic technologies support, the semantic technologies support is automatically upgraded to Release 12.1 or later when the database is upgraded.

However, you may also need to migrate RDF data if you have an existing Release 11.1 or 11.2 RDF network containing triples that include typed literal values of type xsd:float, xsd:double, xsd:boolean, or xsd:time.

To check if you need to migrate RDF data, connect to the database as a user with DBA privileges and query the MDSYS.RDF_PARAMETER table, as follows:

SELECT namespace, attribute, value FROM mdsys.rdf_parameter
  WHERE namespace='MDSYS' 
  AND attribute IN ('FLOAT_DOUBLE_DECIMAL',
                    'XSD_TIME', 'XSD_BOOLEAN', 
                    'DATA_CONVERSION_CHECK');

If the FLOAT_DOUBLE_DECIMAL, XSD_TIME, or XSD_BOOLEAN attributes have the string value INVALID or if the DATA_CONVERSION_CHECK attribute has the string value FAILED_UNABLE_TO_LOCK_APPLICATION_TABLES, FAILED_INSUFFICIENT_WORKSPACE_PRIVILEGES, or FAILED_OLS_POLICIES_ARE_ENABLED, you need to migrate RDF data.

However, if the FLOAT_DOUBLE_DECIMAL, XSD_TIME, and XSD_BOOLEAN attributes do not exist or have the string value VALID and if the DATA_CONVERSION_CHECK attribute does not exist, you do not need to migrate RDF data. However, if your semantic network may have any empty RDF literals, see Handling of Empty RDF Literals; and if you choose to migrate existing empty literals to the new format, follow the steps in this section.

To migrate RDF data, follow these steps:

1. Connect to the database as the SYSTEM (not SYS .. AS SYSDBA) user or another non-SYS user with the DBA role, and enter: SET CURRENT_SCHEMA=MDSYS

2. Ensure that the user MDSYS has the following privileges:

   • INSERT privilege on all application tables in the semantic network

   • ALTER ANY INDEX privilege (optional: only necessary if Semantic Indexing for Documents is being used)

   • ACCESS privilege for any workspace in which version-enabled application tables have been modified (optional: only necessary if Workspace Manager is being used for RDF data)

3. Ensure that any OLS policies for RDF data are temporarily disabled (optional: only necessary if OLS for RDF Data is being used). OLS policies can be re-enabled after running convert_old_rdf_data.

4. Start SQL*Plus. If you want to migrate the RDF data without converting existing empty literals to the new format (see Handling of Empty RDF Literals), enter the following statement:

   EXECUTE sdo_rdf_internal.convert_old_rdf_data;
   

   If you want to migrate the RDF data and also convert existing empty literals to the new format, call convert_old_rdf_data with the flags parameter set to 'CONVERT_ORARDF_NULL'. In addition, you can use an optional tablespace_name parameter to specify the tablespace to use when creating intermediate tables during data migration. For example, the following statement migrates old semantic data, converts existing "orardf:null " values to "", and uses the MY_TBS tablespace for any intermediate tables:

   EXECUTE sdo_rdf_internal.convert_old_rdf_data(
     flags=>'CONVERT_ORARDF_NULL', 
     tablespace_name=>'MY_TBS');
   

   The sdo_rdf_internal.convert_old_rdf_data procedure may take a significant amount of time to run if the semantic network contains many triples that are using (or affected by use of) xsd:float, xsd:double, xsd:time, or xsd:boolean typed literals.

5. Connect to the database as the SYS user with SYSDBA privileges (SYS AS SYSDBA, and enter the SYS account password when prompted). Then enter the following statement:

   • Linux: @$ORACLE_HOME/md/admin/semrelod.sql

   • Windows: @%ORACLE_HOME%\md\admin\semrelod.sql

• Required Data Migration After Upgrade
  
• Handling of Empty RDF Literals
  

Effective with Oracle Database Release 12.2, the following are no longer supported:

• Workspace Manager support for RDF data

• Virtual Private Database (VPD) support for RDF data

If an existing semantic network that contains Workspace Manager (WM) or Virtual Private Database (VPD) data is upgraded, the RDF Semantic Graph installation will be marked as INVALID. In addition, the MDSYS.RDF_PARAMETER table will contain a row with description Feature not supported in current version' for the unsupported component. To correct this situation, all existing WM and VPD data should be dropped, and the WM and VPD components should be uninstalled.

To uninstall Workspace Manager support for RDF data:

1. Connect to the database as the SYS user with SYSDBA privileges (SYS AS SYSDBA, and enter the SYS account password when prompted).

2. Start SQL*Plus, and enter the following statement:

   • Linux: @$ORACLE_HOME/md/admin/sdordfwm_rm.sql

   • Windows: @%ORACLE_HOME%\md\admin\sdordfwm_rm.sql

   Note:

   If you are in a multitenant environment, run the script with catcon.pl. See “Running Oracle-Supplied SQL Scripts in a CDB” in Oracle Database Administrator’s Guide.

To uninstall Virtual Private Database support for RDF data:

1. Connect to the database as the SYSTEM user (not SYS … AS SYSDBA) or as another non-SYS user with the DBA role.

2. Start SQL*Plus, and enter the following statement:

   EXECUTE mdsys.sem_rdfsa_dr.uninstall_vpd;

After performing the necessary uninstall operations, reset the network validity as follows:

1. Connect to the database as the SYS user with SYSDBA privileges (SYS AS SYSDBA, and enter the SYS account password when prompted).

2. Start SQL*Plus, and enter the following statement:

   • Linux: @$ORACLE_HOME/md/admin/semvalidate.sql

   • Windows: @%ORACLE_HOME%\md\admin\semvalidate.sql

   Note:

   If you are in a multitenant environment, run the script with catcon.pl. See “Running Oracle-Supplied SQL Scripts in a CDB” in Oracle Database Administrator’s Guide.

If you need to downgrade to Oracle Database Release 12.1, the RDF semantic graph support component will be downgraded automatically when you downgrade the database. However, any RDF or OWL data that is specific to Release 12.2 (that is, Release 12.2 or later RDF/OWL persistent structures that are not supported in previous versions) must be dropped before you perform the downgrade, so that the database is compatible with Release 12.1.

To check if any Release 12.2 or later RDF data is incompatible with Release 12.1, perform the following steps:

1. Connect to the database (Release 12.2 or later) as the SYS user with SYSDBA privileges (SYS AS SYSDBA, and enter the SYS account password when prompted).

2. Start SQL*Plus, and enter the following statements:

   SET SERVEROUT ON
   EXECUTE SDO_SEM_DOWNGRADE.CHECK_121_COMPATIBLE;
   

If any RDF data is incompatible with Release 12.1, the procedure generates an error and displays a list of the incompatible data. In this case, you must perform the following steps:

1. Remove any Release 12.2 or later release-specific RDF or OWL data if you have not already done so, as explained earlier in this section.

2. Perform the database downgrade.

3. Connect to the Release 12.1 database as the SYS user with SYSDBA privileges (SYS AS SYSDBA, and enter the SYS account password when prompted).

4. Start SQL*Plus, and enter the following statement:

   • Linux: @$ORACLE_HOME/md/admin/catsem.sql

   • Windows: @%ORACLE_HOME%\md\admin\catsem.sql

     Note:

     If you are in a multitenant environment, run the script with catcon.pl. See “Running Oracle-Supplied SQL Scripts in a CDB” in Oracle Database Administrator’s Guide.

   If the script completes successfully, a row with the following column values is inserted into the MDSYS.RDF_PARAMETER table:

   • NAMESPACE: MDSYS

   • ATTRIBUTE: SEM_VERSION

   • VALUE: (string starting with 12.1)

   • DESCRIPTION: VALID

   After the catsem.sql script completes successfully, Oracle semantic technologies support for Release 11.2 is enabled and ready to use, and all Release 12.1-compatible data is preserved.