[archive] Online backups

[Migrated content. Thread originally posted on 08 November 2004]

I have a request from a customer to limit thier data loss to 4 hours or less. This means that there would have to be periodic backups done during the day while users are on the system. Database products I've looked at have an online backup facility but that is not available with the Vision file system. Has anyone attempted to do this, or is it just completely impossible?

I know (at least on windows) there are some commercial backup products that allow file system backup even if files are open and locked by the o/s. They do this via a kernel mode device driver. We use one such product.

Can't really testify if this makes you 100% safe from data corruption. Also, this leaves you open for a race condition if your backup runs during a complex writing process that involves multiple files.

An alternative would be to do daily auditing involving C$REDIRECT and same careful coding. Implementing C$REDIRECT system wide is kind of a pain however.

The best solution of course would be to get your system running on a SQL database which supports replication or PITR...my favorite being postgresql. Their are various options in migrating your COBOL app to a SQL database including purhasing a 4GL license from AcuCorp.

Merlin

[Migrated content. Thread originally posted on 08 November 2004]

I have a request from a customer to limit thier data loss to 4 hours or less. This means that there would have to be periodic backups done during the day while users are on the system. Database products I've looked at have an online backup facility but that is not available with the Vision file system. Has anyone attempted to do this, or is it just completely impossible?

I know (at least on windows) there are some commercial backup products that allow file system backup even if files are open and locked by the o/s. They do this via a kernel mode device driver. We use one such product.

Can't really testify if this makes you 100% safe from data corruption. Also, this leaves you open for a race condition if your backup runs during a complex writing process that involves multiple files.

An alternative would be to do daily auditing involving C$REDIRECT and same careful coding. Implementing C$REDIRECT system wide is kind of a pain however.

The best solution of course would be to get your system running on a SQL database which supports replication or PITR...my favorite being postgresql. Their are various options in migrating your COBOL app to a SQL database including purhasing a 4GL license from AcuCorp.

Merlin

[Migrated content. Thread originally posted on 08 November 2004]

I have a request from a customer to limit thier data loss to 4 hours or less. This means that there would have to be periodic backups done during the day while users are on the system. Database products I've looked at have an online backup facility but that is not available with the Vision file system. Has anyone attempted to do this, or is it just completely impossible?

Is this a Windows implementation?

I'm not necessarily saying this will work for your customer (since I don't know any details), but you could look at using Windows 2003 Server and its File Replication Services (FRS). With FRS, you can have changes made to specific files or directories automatically replicated to another server, so if the primary server failed, they could just switch over to the backup server.

[Migrated content. Thread originally posted on 08 November 2004]

I have a request from a customer to limit thier data loss to 4 hours or less. This means that there would have to be periodic backups done during the day while users are on the system. Database products I've looked at have an online backup facility but that is not available with the Vision file system. Has anyone attempted to do this, or is it just completely impossible?

Hi.

my suggestion is to create a journal file via the c$redirect routine.

Via the c$redirect you intercept every update operation (WRITE, REWRITE, DELETE) and append them on a journal file like this:

01 journal-record.
05 jr-file-name pic x....
05 jr-operation pic x...
05 jr-record-image pic x...

when a system crash occurs, you restore the last vision backup and run a Cobol program that reads the journal file and playbacks in chronological order all the operations occured from the last backup.

at every vision OFFLINE backup, you clear the journal file.

this is (more or less) the way RDBMS perform a "rollfworward" of your transactions.

another way is to use the Vision native transaction management and the c$recovery routine, that provides you rollforward functionality, but i never tried it.

ciao.


The advantage of this solution is thath it works on every operating system.