Microsoft SQL Server 2008 R2 Unleashed- P70 ppt

This immediately launches the Configure Database Mirroring Security Wizard for the database you have selected AdventureWorks, in this example.. FIGURE 20.10 The Principal Server Instance

FIGURE 20.9 Including the witness server instance in the mirroring configuration

You need to click the Configure Security button on the Mirroring page This immediately

launches the Configure Database Mirroring Security Wizard for the database you have

selected (AdventureWorks, in this example) Figure 20.8 shows this initial wizard splash page

You must configure all three server instances (principal, mirror, and witness servers) for

the high-availability mode The first option that must be indicated is whether you plan to

include a witness server instance in your mirroring configuration You are configuring a

high-availability database mirroring configuration (synchronous mode with automatic

failover), so you should select Yes on the wizard dialog shown in Figure 20.9; you do so

because you want to create a full high-availability mode for automated failover

FIGURE 20.8 The Configure Database Mirroring Security Wizard for the AdventureWorks

database

FIGURE 20.10 The Principal Server Instance screen of the Configure Database Mirroring

Security Wizard

endpoint name EndPoint4DBMirroring1430, in this example)

Next comes the specification of the listener and endpoint entry for the mirror server

instance (where the mirror copy of the database will be located) Initially, this page lists all

server instances available on your network (that is, possible mirror server instances) and

does not have a listener port or endpoint name specified yet You need to identify which

server you want to use as the mirror server instance (REM12374333\SQL08DE02, in this

example) and click the Connect button to establish a valid (authorized) connection to the

mirror server instance Because you already set up the endpoint on this server (and

granted connection permission, using a specific login ID), when you complete the

connec-tion dialog, the endpoint (EndPoint4DBMirroring1440, in this example) and

listener_port value (1440, in this example) should be enabled, as shown in Figure 20.11

Finally, you need to specify the witness server instance Again, this dialog page lists all

server instances available on the network (that is, possible witness server instances) and

does not have a listener port or an endpoint name specified yet You need to identify

which server you want to use as the witness server instance (REM12374333\SQL08DE03, in

this example) and click the Connect button to establish a valid (authorized) connection to

the witness server instance Because you already set up the endpoint on this server (and

FIGURE 20.12 The Witness Server Instance screen of the Configure Database Mirroring

Security Wizard

FIGURE 20.11 The Mirror Server Instance screen of the Configure Database Mirroring

Security Wizard

granted connection permission, using a specific login ID), when you complete the

connec-tion dialog, the endpoint (EndPoint4DBMirroring1450, in our example) and

listener_port value (1450, in this example) should be enabled, as shown in Figure 20.12

The last step in the Configure Database Mirroring Security Wizard is to identify any service

accounts that you want to use for the server instances in this database mirroring

FIGURE 20.13 Summary of actions to be performed for the database mirroring configuration

A report is generated, telling the total number of actions taken (three, in this case) and the

status of each action If any errors or warnings result, you can drill down into the Report

button option in the bottom-right corner of this summary of actions page to determine

what has occurred If each status shows success, a Database Properties dialog, as shown in

Figure 20.14, appears when you close this report page This dialog gives you the option to

start mirroring immediately or not start mirroring (because you will start mirroring at

some other time) For this example, you want to start mirroring right away, so click the

Start Mirroring button

FIGURE 20.15 Fully configured properties and active mirroring for database mirroring

Figure 20.15 shows the full Database Properties screen for the AdventureWorks database, all

server network addresses, and the operating mode for mirroring

If you look at the SQL Server log file (that is, the current log), you can see log entries

indi-cating that database mirroring is active:

2/21/2009 22:33:33,spid21s,Unknown,Database mirroring is

active with database ‘AdventureWorks’ as the

principal copy This is an informational message

only No user action is required

2/21/2009 22:33:09,spid17s,Unknown,Starting up database ‘AdventureWorks’

FIGURE 20.14 Specifying to start database mirroring for high safety with automatic failover

FIGURE 20.16 Launching Database Mirroring Monitor from SSMS

Monitoring a Mirrored Database Environment

After active mirroring has started, you can monitor the complete mirrored topology in a

few ways You can start by registering the database being mirrored to a new facility within

SSMS called Database Mirroring Monitor Database Mirroring Monitor allows you to

monitor roles of the mirroring partnership (that is, principal, mirror, and witness), see the

history of transactions flowing to the mirror server, see the status and speed of this

trans-action flow, and set thresholds to alert you if failures or other issues occur In addition, you

can administer the logins/service accounts being used in the mirrored database topology

Figure 20.16 shows how you launch the Database Mirroring Monitor from SSMS: you

right-click the principal database being mirrored, choose Tasks, and then choose Launch

Database Mirroring Monitor

FIGURE 20.17 Registering the mirrored database within the Database Mirroring Monitor

FIGURE 20.18 The registered database and status of each mirroring partner

You must register the database being mirrored To do so, you select the principal or mirror

server instance and set the Register check box for the database Database Mirroring

Monitor registers the database and both partner server instances, as shown in Figure 20.17

After the database is registered, all partners and the witness server instances show up in

the Database Mirroring Monitor, as shown in Figure 20.18

At a glance, you can see which server is playing what role (principal or mirror) and

whether each partner has defined and is connecting to a witness server In addition, you

can see the unsent log (in size), the un-restored log (in size), when the oldest unsent

trans-action occurred, the amount of time it took to send the transtrans-action to the mirror server

instance, the send rate (KB/second), the current rate at which the transactions get restored

FIGURE 20.19 Transaction history of mirroring partners

If you click the Warnings tab of the Database Mirroring Monitor, you can set various

thresholds within the monitor to alert you when they have been reached (see Figure

20.20) Basically, you want to set thresholds that monitor the effectiveness of the

mirror-ing operation

If these key thresholds are ever exceeded, you want to be notified that something is very

wrong and that failover may be in jeopardy When a threshold is exceeded, an event is

logged to the Application event log You can configure an alert on this event by using

SSMS or Microsoft Management Operations Manager (MOM) The threshold levels depend

on your own failover tolerance Our advice is to monitor the transaction and transfer rates

for a peak period and then set the thresholds to be 100% higher than that For example, if

you see a peak mirror commit overhead value of 750 milliseconds, you should set the

threshold to 1,500 milliseconds This should be within the tolerance for commit overhead

in your organization

Figure 20.21 shows how easy it is to administer the service accounts/login IDs being used

for database mirroring You simply click an Edit button to change or set the login account

you want to use for database mirroring at each instance in the mirroring topology

FIGURE 20.21 Setting service accounts/login IDs within the mirroring topology

FIGURE 20.20 Setting thresholds to monitor mirroring effectiveness

From the Database Properties Mirroring page, you can easily pause (and resume) database

mirroring if you suspect that there are issues related to the mirroring operation In

addi-tion, you can easily see what role each server instance is playing

FIGURE 20.22 Removing database mirroring

Looking at the options on Figure 20.22, you simply choose to remove mirroring (from the

principal server instance) This is just a bit too easy to do—almost dangerous!

The mirroring process is immediately disabled When mirroring is disabled, you can drop

the database on the mirror server instance, remove the endpoints on each server instance

(that is, principal, mirror, and witness instances), and be done—all through SSMS This

approach is straightforward

If you’re removing mirroring with SQL scripts, however, you need to break the mirroring

from the principal, remove the principal’s endpoint, drop the mirror database and remove

the mirror’s endpoint, and then drop the witness server’s endpoint At this point, all

mirroring is removed Follow along as we remove the database mirroring configuration we

just set up