NonStop SQL DDL Replicator User's Guide (Update 6)

SDR Operations

HP NonStop SQL DDL Replicator User’s Guide—545799-006

4-8

SDR Updater Processes

The SDR monitor is responsible for monitoring all RDF activity. It does so by

monitoring RDF events sent to collector $0. The SDR monitor also makes a periodic

check of RDF and eventually makes the proper adjustments, even if the RDF events

are not available. When the SDR monitor detects an active RDF subsystem, it starts an

SDR updater process on the RDF backup system.

The SDR updater monitors events sent to the EMS collector that is configured as the

RDF LOGFILE. Although RDF always sends events to both $0 and any configured

LOGFILE, some installations might have a filter to eliminate RDF events. The SDR

updater depends on analyzing RDF events for proper operation.

Although the SDR updater is started and managed from the primary RDF system, the

SDR monitor must also be executing on the backup system.

Each SDR updater manages a specific RDF configuration. By RDF configuration, we

refer to the configuration identified by an RDF control subvolume of format node[suffix-

character]. If there are multiple active RDF control subvolumes, the SDR monitor will

start multiple SDR updater processes, one for each control subvolume. For example, if

on system \PRIM there are RDF control subvolumes PRIMA and PRIMB, there will be

two SDR updaters on the backup system, one for PRIMA and one for PRIMB.

Normal vs. Takeover Operations

When RDF is operating in normal mode, the SDR monitor on the primary RDF system

manages the SDR updater on the backup system. When RDF is operating in takeover

mode, it is assumed that the primary system is unavailable; the SDR monitor on the

backup system manages the SDR updater.

EMS Messages

In contrast to RDF, each SDR component, including the SDR updater, logs all EMS

events to the system that it was started from. When RDF is in normal mode, all SDR

EMS events are sent to the primary system EMS collector. When RDF is in takeover

mode, all SDR events are sent to the backup system EMS collector. This maintains a

better time line of all SDR events and avoids problems comparing primary and backup

EMS logs.

Replication Operations

Replicating and executing DDL statements entails the following operations:

Creating the SDR Depot Files on the Backup

Processing Stop RDF Update Audit Records

Translating DDL

Executing DDL