From: Simon Fox [mailto:[EMAIL PROTECTED]]
> What is the recommended procedure for a live system regarding backups
> and restores. I am currently doing the following:
>
> I am creating 3 backup mediums as follows:
> The first for a complete backup which will be done nightly.
> The second for an incremental backup to done reguarly through the day
> The third as an auto log backup
>
> dmcli commands as follows:
> backup_media_put data c:\datasave FILE DATA 0 8 YES
> backup_media_put auto c:\autosave FILE AUTO 0 8 YES
> backup_media_put pages c:\pagesave FILE PAGES 0 8 YES
> util_connect dbm,dbm
> autosave_on
> quit
>
> When doing a complete backup, I do the following:
> util_connect dbm,dbm
> backup_start data RECOVERY DATA
> util_release
Using each time the same medium (file) for a data backup
is risky because during the backup you do not have a
valid backup of your database.
By the way
dbmcli -d ... -u ... -uUTL -c backup_start data RECOVERY DATA
is the same.
> When doing the incremental backups I do the following:
> util_connect dbm,dbm
> backup_start pages RECOVERY PAGES
> util_release
If you perfom more than one incremental backup you have
to use different files for your backups. An incremental
backup contains only the data written after the last
complete or incremental backup.
> It is my understanding that if autolog is turned on, then you do not
> need to perform manual log backups.
You do not need manual backups. It is even not possible to
perform a manual log backup if autolog is turned on.
> If this is the case, shouldn't you see files on the file system
> corresponding the file name in the medium , ie. \pagesave??
SAP DB appends a version number to log backup. You should see
files like c:\autosave.001 c:\autosave.002 ...
Therefore it is important to monitor your hard disk because
the log backups will fill your disk.
An automatic log backup starts if a so called "log segment" is
full (see also the database parameter LOG_SEGMENT_SIZE). Maybe
you do not have enough stuff in your log.
The autolog_on command sets only a flag in the database. If
there is later a problem during the real backup the database
turn the autolog off and write a error message to the
knldiag.err file.
Check your autolog state with the DBMServer command autolog_show.
> Should Autolog be on in a live system?
It is a feature. You may use it or not. With autolog you have
a better protection against the "log full" situation.
> If you do automatic log backups, then is there any need to do
> incremental backups (ie. PAGES) and vice versa, ie. if the
> log is backed up, is there any need to do incremental backups?
Lets have a example. You have the follwing backups of
your database (C for complete, I for incremental and L
for log):
C1 L1 L2 I1 L3 C2 L4 I2 L5 L6 I3 L7
There are 5 possible recovery strategies:
1. C1 L1 L2 L3 L4 L5 L6 L7
2. C1 I1 L3 L4 L5 L6 L7
3. C2 L4 L5 L6 L7
4. C2 I2 L5 L6 L7
5. C2 I2 I3 L7
(Normally you should use 5.)
The backup/recovery strategy (how often and which types of
backups) depends on your application profile. There is no
general answer.
Bernd
--
SAP Labs Berlin
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