I'm interested in how Combining Log Shipping and Database Mirroring works when failover occurs.
From SQL BOL, it says:
"Topic: Database Mirroring and Log Shipping
...
To run in high-safety mode with automatic failover the mirroring
session is configured with an additional server instance known as the witness.
If the principal database is lost for any reason after the database is
synchronized and if the mirror server and witness can still communicate
with each other, automatic failover occurs. An automatic failover
causes mirror server to assume the principal role and bring its
database online as the principal database. For more information, see Automatic Failover
[ http://msdn2.microsoft.com/en-us/library/ms189590.aspx ] . If the log
shipping backup location is accessible to the new principal/primary
server, its backup jobs begin to ship log backups to that location. The
database mirroring synchronous mode guarantees that the log chain is
unaffected by a mirroring failover and that only valid log is restored.
The secondary servers continue to copy log backups without knowing that
a different server instance has become the primary server.
..."
Source: http://msdn2.microsoft.com/en-us/library/ms187016(d=printer).aspx
Could anyone tell me that how the database mirroring synchronous mode guarantees that the log chain is
unaffected by a mirroring failover and that only valid log is restored?
Let me elaborate the situation (if anything I said is incorrect, please correct me )
Here is the time line of the failover happens:
------- tn-1 ---------- tn ---------- tf -------- tn+1 ---------------> t
----------------> t: the time line.
tn: the moment that the log shipping backup job and copy job is done for the transaction log obtained between the time interval tn-1 and tn.
tf: the moment that mirroring failover occurs in the database mirroring session.
the time interval between each tn and tn-1 are constant, say h seconds, for all n are positive integers.
Here is the question that I want to ask:
In database mirroring synchronous mode, it guarantees that all the committed transaction from the moment tn to tf is copied to the mirror database. All the transaction log backup for log shipping are done on the original principal before the moment tf. After the mirroring failover occurs at the moment tf, how the log shipping mechanism guarantees that the transaction log between the interval tn and tn+1 that can be unaffected by a mirroring failover?
That's the point that I interested in.
I'm looking at replicating our primary SQL server to a secondary offsite server (linked via 100Mb so effectively LAN speed). What are people's preference when deciding on a solution?
On the surface mirroring looks much better but having dug a little I've found it is recommended only 10 databases are mirrored per instance. That said, I've found a post from someone who is upto 58 databases mirrored. Are there similar limitations with log shipping?
Does anyone have any experience of mirroring and is using it in prefence to log shipping?
Our current recovery strategy is the classic restore the SQL dump from tape onto a rebuilt server so either method will be a vast improvement. None of our databases are mission critical that they need upto the second replication. 15 minute replication would be fine leading me to think that log shipping may be better given the possible limitations of mirroring
For recovery, I was considering amending the DNS records of the Database servers. Does anyone see any issues with this approach? I understand there is a automatic failure function if using mirror but this may require the application to be coded correctly?
Up to now we have gotten by without having any local DR copies of servers (if a sql server goes down we are usually able to get it back in less than 3 hours). But I want more now. I want to trim the "down" window to no more than 5 or 10 minutes. (Immedate failover would be nice but is not an essential requirement. The essential requirement is to loose no data!)
I have a spec of knowledge in these areas:
SQL 2005 Clustering (requires approved hardware, quorum disk, etc. involved)
SQL 2005 Replicaiton
SQL 2005 Log Shipping.
SQL 2005 Database mirroring. ( needs three servers)
Which approach do you think is the most straightforward, sparing of hardware, yet reliable way to get us back up and running after a sql server failure.
Can anybody tell me the differences, advantages and disadvantages between these three solutions? When do I may use one or another? Could you recommend me any documentation?
I am confuse and cant decide on how to setup high availability on our SQL 2005. Here's what on my mind and on resources list:
I plan to have mirroring on my SQL1 to SQL2 with the help of SQL3 as witness. So this would be automatic failover. My idea on mirroring is when SQL1 goes down, SQL3 would tell SQL2 to run and be the primary. It will automatically failover to SQL2. Right? My questions are:
1) How can I revert back to SQL1 once it is ready?
2) I read in one of the post that it is impossible to write in a mirrored DB, is this true? I mean, what's the use of failing over to the next node when it's not possible to write and update data/records?
3) If number 2 is false (i hope so), how would the data be synchronize from SQL2 back to SQL1. Those transaction that were made while SQL1 is down.
4) How about the connection string from the web applications? Would it be automatically point to SQL2? We have load balancing setup in place, would this help web application connection to automatically point to SQL2?
Another setup:
We have SAN in place (not yet used, but is planning to use for this SQL thing), EMC to be specific. My question would be:
1) For SAN setup, the data storage would be centralize. So would that mean that SQL1 and SQL2 services will use the same data and log file from the SAN storage?
2) How would you call this setup then? Can this be clustering type of high availability? Will clustering work under load balancing setup? I believe mirroring is not possible here? Right?
3) How can I setup my 3 SQL servers with the same theory in mind: when SQL1 goes down, SQL2 will take over. Data will be synchronize when SQL1 is up and running again. With automatic failover and reverting back to primary.
I read so much topics about this, but the more I research, the more I get confuse.
Any suggestions, comments, advice is greatly appreciated!
Using SQL Server 2008, we would like propose mirroring between two servers of a critical database. Since we initiate, may require to clarify on its purpose and also required changes from application end.Any changes required from OS Level? (I believe both servers IP or Host name should be added in host entries. Mirroring ports should be allowed/open including Principal and mirror server IP Addresses): Windows Team.Any changes required from Application? (Instance name, authentication: user name and its password should be added in web config files): Application Team.Any changes required from Network Team?Also for mirroring both the principal and mirror servers should be with same version, does it only mean SQL Server 2008 versions are enough or does it also mean to say build numbers 10.00.4000 should also be same.URL....
I have just finished configuring my first test mirrored environment (High safety mode). I setup the database engine service accounts on each of the servers with domainuser. I inherited a production mirrored environment set up by someone else. On the production servers the database engine service account is NT Authorityuser a local account. I am trying to practice installing Windows updates within a mirrored environment and I not sure how to proceed when the service account is NT Authority user account. should I change the service account to a domainuser?
ALTER DATABASE foo set PARTNER = 'TCP://10.3.3.1:1234' I get this error message:
The database is being closed before database mirroring is fully initialized. The ALTER DATABASE command failed. What does that mean, and how do I fix it?
I set up a new mirror server. Everything is good except that the Database Mirroring Monitor is not working for one of the databases. In the monitor the principal data is showing up as blank
If I look at dbm_monitor_data on the principal most of the data columns (e.g. Send_queue_size) are null where as they have data for the other databases.
Both servers are SQL Server 9.0.2047 Enterprise Edition.
We have a user Training database that we would like to keep updated from our Production database. Users would make different modifications to the Training and Production databases. It is the user updates on the secondary that bother me and I have not seen anything that indicates Log Shipping would fail if new random records are added to both the secondary and primary.
Would Log Shipping be appropriate for this nightly update of Training from Production?
In order to move from one data center to another, I am planning to use log shipping. Lets say,
Current Data center - DC1 Current Server- S1 Current Database- DB1
New Data Center -DC2 New Server -S2
Now, on the New Server S2, I already restored DB1 as DB1 for QA testing. QA has to do some testing before we move from DC1 to DC2. In the mean time, I need to start log shipping from S1 to S2, so that we can fail-over to S2. Now since DB1 database is already present on S2, I can not use the same name. I will have to use some other name (say DB1_New). I can not wait for QA to finish their testing. I have to start log shipping before that. When QA is done, I will delete the DB1.
So for this log shipping, -
Primary - S1- DB1 Secondary - S2 DB1_New
So when we fail-over, we will have the database name as DB1_New. But all the apps use the name DB1. So I will have to rename the database as DB1.
So want to know, will this renaming the database (DB1_New to DB1) cause any issues?
I could not able to find Forums in regards to 'Log Shipping' thats why posting this question in here. Appriciate if someone can provide me answers depends on their experience.
Can we switch database recovery model when log shipping is turned on ?
We want to switch from Full Recovery to Bulk Logged Recovery to make sure Bulk Insert operations during the after hours load process will have some performance gain.
I have read on the web that high protection mode not recommended, except in the event of replacing the existing witness server. But I can't find the reason why anywhere. Can anybody explain? Thanks.
1. Once the mirroring is setup is it possible to switch between high-protection and high-performance modes? If it is will I have to stop the mirroring, switch the modes and then restart it again?
2. Let's say the principal server went down and I manually failed over to the mirror server. Mirror server runs as a new principal server for a couple of days and then I bring the original principal server back up. What needs to be done in order to bring transactions on the principal server up to date?
for a database mirroring , which stretergy is good. Creating with witness server or without it.?
I am firsttime doing this , so i am posting it to the forum..
and also if we are creating the database mirroring with witness server for automatic failover , will the witness server need the same amount of harddisk space like the pricipal or mirror server.??
we want to migrate our production server , without taking the database down.so what we did was , we mirrored the databases from production to one of our development servers and we took the prodcution server for uprgrade.
so today we are moving back (mirroring) all the databases from that development server to our new production server.
my question is , when i move
productionserver_old(principal server) - having the script for principal server
development server(mirror server---->principalserver)) - having the script for mirror server , which is now acting as principal server
new production server(mirror server) - having the script for mirror server. will become principal server , once i moved all the databases
now while mirroring between the developement server and the new production server, i have to run the scripts for the mirror server only.
so both the servers are havign the mirror script now...
is that a problem, or any other way i can handle this....
Does anybody know any good Tutorials for Database Mirroring (Automatic Failover) or Manual Sync with Mirror Server. I tried some sites online, but doesn't have detailed steps.. pls.help as i need to sync data with One of my Mirror using Sql Server 2005.
I have some questions about database mirroring. we have almost 40 databases in one server. Can I set up the database mirroring for all the databases. Is it going to any affect on performance. we have already setup the mirroring on almost 30 databases, and I need to set up for the rest of 10. please some body could help on this. Thank you.
Hi, i'm a novice of sql server and I have a problem. I have to reply a server in which there are database that are managed with sql server 2000 sp3; what I must make in order to set up the mirroring between the database of the two server so that the data are always aligned ?
I am new user of SQl and preparing the exam database mirroring....can you tell me how i start the mirroirng ..what is my first tep..and is there only one instance
1. Once the mirroring is setup is it possible to switch between high-protection and high-performance modes? If it is will I have to stop the mirroring, switch the modes and then restart it again?
2. Let's say the principal server went down and I manually failed over to the mirror server. Mirror server runs as a new principal server for a couple of days and then I bring the original principal server back up. What needs to be done in order to bring transactions on the principal server up to date?
Can we have database mirroring for two databases. Like i have an application where in the db used are two, namely DB1 and DB2, DB1 is used in the connection string and with the help of DB1 the tables and sps of DB2 are handled.
in this case can i go ahead with database mirroring. Please comment and give the idea or link on the same.
I have some trouble with shipping my transaction logs to the secondary database be it on
another server or within the same server to another database instance.
Im using SQL Server 2005 workGroup editions with Service Pack 2.
Here are the problems that i encountered.
I do hope someone has bumped into such a problem and willing to help me out.
I tried on 2 separate servers (not domain environment) and also between 2 separate instances (which is supposed to be simple!) on our development server,but was unsuccessful.
Between 2 separate instances on the development server - No error after configuring Log shipping though. The configuring went through and it was a success. Transaction logs was backup every minute and it got copied over to the other folder. But SQL Agent not doing its last job which is supposed to restore to the secondary database on another instance.No errors given out in SQL Agent error log files.Anywhere else im supposed to look to see if there are errors given out? Both instances SQL Agent has the same log on username and password with Administartive rights
So what went wrong?
Between the 2 servers- The transaction logs was backup every 1min on the primary server but it didn't got copied over to to the secondary database. - Error message given was:Error in restoring database to the secondary database.Network path given could not be found. Can't open the AxTest.bak file. (i am very sure i have type the correct network path,even have shared it out and i think the firewall is blocking incoming traffic since unlike our development server, which allows us to access when we use Start>Run and type in the ip address,user name and password,the primary server will only tell me no network path was found) I also believe it's because the SQL Agent on the secondary database server wasn't given permission to access the primary database folder. I've shared out the drive and folder on the secondary server and even have allowed SQL Agent to read,write and modify on both servers. For the primary and secondary SQL Agent, I configure their log on to be the same user account name and password which have administrative rights. So what went wrong?
Isit really true that both servers have to be in domain environment before you can configure log shipping,mirroring and replication?
Hope someone help me out of this predicament.Thank you in advance!
