From time to time we need to clone/duplicate some databases and we have several ways to do that, most common are duplicate and restore (with a new name) commands. But when using RMAN catalogs we need to take extra care because we can up lose the backups of the entire database because of the wrong way to do that. And this is even more crucial when using ZDLRA.
You need to choose between The Good and The Bad. Because if you choose wrong you will have troubles with The Ugly. The key factor here is the RMAN/ZDLRA catalog, choose wrong and you will automatically add bad data in the internal catalog tables and if you will try to clean, can delete database backups.
In this post, I will show how correctly clone one database when you are using the RMAN/ZDLRA catalog and the reasons for that. I will show the problems and the collateral effects for ZDLRA when you choose the bad way.
When we are enrolling a database at ZDLRA we need to configure the RMAN channel parameters to point to our definitions like RA_WALLET and CREDENTIAL_ALIAS. The same is done for backup and restore channels. But this can be done in a different way using RA_CLIENT_CONFIG_FILE for ra_library.
As I wrote previously, sometimes we need to have long-term/archival backups due to some compliance. And usually, these backups are stores outside (like a vault/bunker) but for sure not at the same datacenter as the database. But how we can do this at ZDLRA?
In my post about COPY_BACKUP, I wrote how to have an external copy of one backup set at ZDLRA. But this is not the best option when we need to archive some backup because it continues to follow the same recovery window as the original backup set. This means that if you need to have some kind of archive for 5 years, you need to define your recovery window (at the policy level) to this window. And for sure this will put high pressure on space usage because all backups will be stored until became obsolete.
So, the best way is to use the KEEP backups from rman. And as I wrote in my previous post, they not interact/broke with the incremental forever strategy. Is possible to generate the keep backup, and using the DBMS_RA.MOVE_BACKUP moves these backups to a filesystem destination (and further you can copy/store) and archive it outside of ZDLRA.
KEEP backups from rman are used to provide long-term and archival retention. They are used to bypass the default policy retention and are used to sustain some regulations/compliances (like HIPAA, or others) that require archival retention. But with ZDLRA they are treated in a different way. Here I will show how the KEEP backups can impact your backup strategy for ZDLRA.
As you know, ZDLRA is one appliance dedicated to provides you zero data loss in several (planned and unplanned) outages. All the backups are stored inside of the delta store to be processed, and they are deconstructed, meaning that the rman backup set does not exist (as is the formal backup set file).
But sometimes we need to copy/extract some backups outside of ZDLRA and copy it to the filesystem. Maybe because some regulations/compliances need to store for long-term/archival purposes. But some caveats are important to be explained.
Survive to disk failures it is crucial to avoid data corruption, but sometimes, even with redundancy at ASM, multiple failures can happen. Check in this post how to use the undocumented feature “mount restricted force for recovery” to resurrect diskgroup and lose less data when multiple failures occur.
Diskgroup redundancy is a key factor for ASM resilience, where you can survive to disk failures and still continue to run databases. I will not extend about ASM disk redundancy here, but usually, you can configure your diskgroup without redundancy (EXTERNAL), double redundancy (NORMAL), triple redundancy (HIGH), and even fourth redundancy (EXTEND for stretch clusters).
If you want to understand more about redundancy you have a lot of articles at MOS and on the internet that provide useful information. One good is this. The idea is simple, spread multiple copies in different disks. And can even be better if you group disks in the same failgroups, so, your data will have multiple copies in separate places.
As an example, this a key for Exadata, where every storage cell is one independent failgroup and you can survive to one entire cell failure (or double full, depending on the redundancy of your diskgroup) without data loss. The same idea can be applied at a “normal” environment, where you can create failgroup to disks attached to controller A, and another attached to controller B (so the failure of one storage controller does not affect all failgroups). At ASM, if you do not create failgroup, each disk is a different one in diskgroups that have redundancy enabled.
For ZDLRA, the task type INDEX_BACKUP it is important (if it is not the most) because it is responsible to create the virtual full backup. This task runs for every backup that you ingest at ZDLRA and here, I will show with more details what occurs at ZDLRA: internals steps, phases, and tables involved.
As you saw in my previous post, ZDLRA opens every backup that you sent and read every block of it to generate one new virtual full backup. And this backup is validated block a block (physically and logically) against corruption. It differs from a snapshot because it is content-aware (in this case it is proprietary Oracle datafile blocks inside another proprietary Oracle rman block) and Oracle it is the only that can do this guaranteeing that result is valid.
ZDLRA tables are owned by rasys user and are one extension of rman recovery catalog views. The internal tables that were added are just a few, but are important to understand how tasks works (mainly INDEX_BACKUP). In this post, I will show tables like plans, plans_details, blocks, and chunks. And besides that, show a little glimpse about how the files are stored.
If you check, officially, the rman recovery catalog already includes some columns from ZDLRA, the column VB_KEY identify the virtual backup key inside ZDLRA. It exists in RC_BACKUP_PIECE as an example. The extra tables added are linked with SBT tasks (clone to tape or cloud), replication (to other ZDLRA), storage (chunks), vbdf and plans (virtual full backup).
One of the most knows features of ZDLRA is the virtual full backup, basically incremental forever strategy. But what this means in real life? In this post, I will show some details about that and how interesting they are, check what it is Virtual Full Backup and Incremental Forever strategy for ZDLRA.
This post is based on my previous one where I showed all the steps to configure the VPC and enroll database at ZDLRA.
Virtual Full Backup
A virtual full backup appears as an incremental level 0 backup in the recovery catalog. From the user’s perspective, a virtual full backup is indistinguishable from a non-virtual full backup. Using virtual backups, Recovery Appliance provides the protection of frequent level 0 backups with only the cost of frequent level 1 backups.
This definition (and image) are in the Zero Data Loss Recovery Appliance Administrator’s Guide and I think that represents the essence of the virtual full backup. ZDLRA receive the incremental level 1 backup, index it, and generate a level 0 to you that it is indistinguishable from a normal backup level 0.
ZDLRA it is an Oracle dedicate appliance specialized to manage your backups, but more than that, provide you zero data loss. I already made an introduction about ZDLRA in my previous post and here I will show how to use and enrolling protected database at ZDLRA: enroll database, create policies and access with rman. Understand how to use ZDLRA, at least the starting point.
Every project starts with scope definition, steps, and requirements. It is not different for ZDLRA project, it is a big appliance, expensive, and integrate a lot of things in just one place: backups, archivelogs, redo, replication, and RPO. The requirements vary from project to project, I will not discuss that here. But will show you the tech part about the usage.
The post has two divisions, the first it is the technical part. You can check how to do that. The second contains the information/documentation part, where I will show more details about the steps.