To start I setup a test table and fill it with some data. From this point in time on, complete data backups are possible.” If a snapshot exists, no complete data backup is possible.Įvery request of this kind is rejected with a notification that a data backup is still in process.ĭrop a database-wide snapshot. “Examples of SQL Statements for Data SnapshotĬreate a database-wide snapshot based on a transactional consistent savepoint similar to the data backup. Just there I also found this interesting remark that I will check out later in more detail: System Administration and Maintenance Informationġ3.14 SQL Syntax for Backup and Recovery.ġ3.14.4 SQL Statements for Data Snapshot……………………………………188 The commands I use I found in our documentation: And off we go – my annotated HANA snapshot walkthrough: Well, then let’s see what the snapshot is like with HANA. Obviously, if you do change a lot of the data that is part of the snapshot, the data area usage will grow quite a bit, even if you’re only doing UPDATEs or DELETEs (funny effect, isn’t it? □ ). Since savepoints can be recovered transactionally consistent by their design, HANA can simply switch back to a saved Converter version and resume working from there.īy knowing this, the answer to the question is easy to give: the data is still in the data area and won’t be overwritten. Having these two concepts savepoint+converter in place, a snapshot is now easy to create.Īll you’ve to do is to keep a specific state of the Converter and keep all pages referenced by this converter version from being overwritten.Īnd that’s exactly what happens within HANA when you take a snapshot. To keep track of which pages are current and which ones can be overwritten, HANA uses a mapping structure called the converter (hello MaxDB again). Instead the old version of the page remains in the storage until one of the subsequent savepoints overwrites it with newly changed data. The old page is not immediately overwritten. That means that whenever a changed data page is written from memory to the disks (this is called a savepoint in HANA) the changed page is stored at a different physical position. Similar to many filesystems and in fact very similar to MaxDB HANA’s persistency employs the shadow paging concept ( ). Ok, let’s answer this obvious question first. Therefore, this little walktrough involves a bit of typing and reading… But, wait a minute: where is all the old data stored then? Unfortunately there is no frontend UI support for HANA snapshots (yet – no idea whether this is on the backlog for development). Great, show me the button for that in HANA studio! So, I can take snapshots of my HANA instance? The HANA implementation is quite close to the MaxDB feature. Those of you that know SAP MaxDB snapshots will clearly recognize the concepts. SAP HANA is offering a pretty similar functionality. The system is ‘frozen’ for a moment, a snapshot is taken and afterwards you can continue to work with the system.įrom that moment on you always have the option to ‘flash back‘ to the system state when you took the snapshot. VMWare, VirtualBox or Parallels) you know how snapshots work: If you’ve worked with a virtual machine (e.g. You restore a backup taken earlier, right?Ī disadvantage of this approach is that it takes a lot of time as the whole database backup needs to be read from the backup medium and be written to the database storage.Īnother way to deal with this requirement is to take snapshots of the database and set it back to a snapshot once required. So, how do you achieve this with a database? One important thing when performing tests is that you repeat them in the same environment (and maybe alter one thing at a time). If this is not the case in your project, please go and talk to your project responsible right away! □ Stil here? Ok, so you’re actually want to perform some testing? Based on revision 45 (SPS 5) of SAP HANA Studio and DatabaseĪs projects with HANA (just like with any other technology) move on, at some point in time the requirement to perform tests and trainings comes up.
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