Designing the event control table

You use the event facility to manipulate the target Datareplicator's operations from the source Datareplicator.

To use the event facility, you must specify in the target environment definition for the target Datareplicator the processing that is to correspond to each event code. For details about how to specify event codes for the target Datareplicator, see 4.7.3 Designing the import procedure.

To use the event issuing facility, execute the hdeevent command at the source Datareplicator with an event code specified. The hdeevent command issues an SQL statement to the event control table and outputs update information for event control to the system log file. The source Datareplicator extracts this update information for event control and sends it to the target Datareplicator in order to manipulate its processing. Immediately upon detection of update information for event control, the source Datareplicator starts transmission to the target Datareplicator without waiting for the transmission interval. After the transmission processing is completed, the source Datareplicator waits for the next transmission interval.

You must create an event control table at the source HiRDB before starting the source Datareplicator.

Organization of this subsection: (1) Event code specification range; (2) SQL statement issued when the hdeevent command is executed; (3) Conditions of the event control table

(1) Event code specification range

Range	Action
0	Terminates the transmission process (information is not sent to the target Datareplicator).
1 to 255	Sends the specified event code to the target Datareplicator.
Other	Information is not sent to the target Datareplicator.

(2) SQL statement issued when the hdeevent command is executed

When you execute the hdeevent command, the SQL statement shown below is issued to the source HiRDB. If the source HiRDB is a parallel server, the SQL statement is issued to all back-end servers.

LOCK TABLE "hde_dtbl" IN SHARE MODE
UPDATE "hde_dtbl" SET EVNO = user-specified-event-code
COMMIT WORK

Instead of executing the hdeevent command, you can issue a similar SQL statement directly to the target Datareplicator. However, you must not take any other action using the event control table.

(3) Conditions of the event control table

The following describes the conditions for creating an event control table before starting the source Datareplicator.

(a) Creator's user ID

Create the event control table with any user ID.

When you execute the hdeevent command, you will specify the user ID used to create the event control table. If you omit the user ID when you execute the hdeevent command, the value of the PDUSER environment variable will be assumed.

(b) Table name

The table name is always hde_dtbl.

(c) Table attribute

Specify the FIX attribute.

(d) Table structure

The following table shows the structure of an event control table.

Table 4-35 Structure of an event control table

Column name	Column attribute	Column length	Value
KEY	INTEGER	1	integer
EVNO	INTEGER	1	0
SNDID	CHAR	10	'0'

(e) Examples of event control tables

When the source HiRDB is a single server
When the source HiRDB is a single server, you create a table consisting of one row. The following figure shows an example of an event control table when the source HiRDB is a single server.

Figure 4-37 Example of event control table when the source HiRDB is a single server
When the source HiRDB is a parallel server
When the source HiRDB is a parallel server, you create a table with one row for each key range partition at each back-end server subject to extraction processing. You must specify one RDAREA for each back-end server. The following figure shows an example of an event control table when the source HiRDB is a parallel server.

Figure 4-38 Example of event control table when the source HiRDB is a parallel server

(f) Notes

You must create the event control table before executing the hdeprep command.
If the source HiRDB is a parallel server and a change is made to the configuration, such as by adding or deleting back-end servers, you must re-create the event control table. Otherwise, no events will be issued for extractions from an added back-end server, resulting in loss of conformity between the source and target databases.
If you have re-created the event control table, re-execute the hdeprep command.
Do not create any table named hde_dtbl in the source HiRDB system other than the event control table.
The event control table is not subject to extraction processing.
If multiple events with an event code in the range 1 to 255 are issued within the same transaction, only the last event issued is effective.

4.6.7 Designing the event control table