Warm Standby Requirements and Restrictions

There are several requirements and restrictions that apply to all SAP Replication Server warm standby applications.

You must use a data server such as SAP ASE, that supports warm standby applications.
One SAP Replication Server manages both the active and standby databases. Both the active and standby databases must be SAP ASE databases. See Heterogeneous Warm Standby for Oracle in the SAP Replication Server Heterogeneous Replication Guide for detailed information on how to set up and configure a warm standby application between two Oracle databases.
You cannot create a standby database for the RSSD. You can create a standby database for the master database only if the SAP ASE supports master database replication, such as SAP ASE 15.0 ESD #2 and later.
SAP Replication Server does not switch client applications to the standby database.
You should run SAP ASE for the active and standby databases on different machines. Putting the active and standby databases on the same data server or hardware resources undermines the benefits of the warm standby feature.
Although SAP ASE allows tables that contain duplicate rows, tables in the active and standby databases should have unique values for the primary key columns in each row.
The commands and procedures for abstract plans are replicated, except for:
- The and set @plan_id clause of create plan is not replicated. For example, this command is not replicated as shown.
```
create plan "select avg(price)
from titles" "(t_scan titles)
into dev_plans and set @plan_id
```
  Rather, it is replicated as:
```
create plan "select avg(price) 
from titles" "(t_scan titles)
into dev_plans
```
- The abstract plan procedures that take a plan ID as an argument (sp_drop_qplan, sp_copy_qplan, sp_set_qplan) are not replicated.
- The set plan command is not replicated.
Failover support is not a substitute for warm standby. While warm standby keeps a copy of a database, SAP Failover accesses the same database from a different machine. Failover support works the same for connections from SAP Replication Server to warm standby databases.

See Using SAP Failover in a High Availability System in the SAP ASE documentation set.
You cannot use the dump and enable marker on the active database and then use cross-platform dump and load to rebuild the standby database. The SAP Replication Agent must send the dump marker to the standby database you are rebuilding. During the cross-platform dump and load, the active database must be in single-user mode when you obtain the dump from the active database.