Kbase P178101: Backup file size is smaller than expected based on messages written to database log file.
| Autor |
Progress Software Corporation - Progress |
| Acesso |
Público |
| Publicação |
30/11/2010 |
|
Status: Unverified
SYMPTOM(s):
Backup file size is smaller than expected based on messages written to database log file.
The total amount of active blocks in the database from prostrct statistics output is 1963337 * 8192 (which is the db block size) seems to indicate that the back up should be about 15 GB.
Actual size of the back up file is a little more than 12 GB.
Database log file indicates that the backup is going to use 15 GB worth of media.
Command used to backup the database: probkup online dbname backupfilename -com -Bp 10.
FACT(s) (Environment):
The database block size is 8192.
Database restores from the backup without any errors.
All Supported Operating Systems
Progress/OpenEdge Product Family
OpenEdge Category: Database
OpenEdge Database Category: Maintenance
CAUSE:
This is expected behavior. The command being used to backup the database is making use of the -com parameter. The -com parameter compresses the database prior to writing it to the backup media. The unused portion of index and record blocks is compressed to a 3-byte compression string. Free blocks are compressed to the length of their header, 16 bytes.
If you specify the -com parameter and do not use the ?scan parameter, PROBKUP displays the number of blocks and the amount of backup media required for an uncompressed database.
FIX:
For a more accurate indication as to how much media is going to be required for the database backup, include the -scan parameter on your backup command line.
The following is sample output from multiple probkup commands of a sports2000 database. The backup commands are issued first without the -com parameter. The second example makes use of the -com parameter without the -scan parameter. The final example makes use of the -com and -scan parameter. Pay close attention to the lines that contain an (**) to see the difference in amount of media needed for the backup.
proenv>probkup sports2000 test.back ?scan (This one is done without compression. Notice the lines with the **)
OpenEdge Release 10.2B as of Mon Dec 14 17:02:01 EST 2009
1347 active blocks out of 1651 blocks in sports2000 will be dumped. (6686) **
0 BI blocks will be dumped. (6688)
The block size is 4096. (6994)
Backup requires an estimated 5.4 MBytes of media. (9285) **
Restore would require an estimated 1347 db blocks using 5.3 MBytes of media. (9286) **
Backed up 1347 db blocks in 00:00:00
Wrote a total of 40 backup blocks using 5.3 MBytes of media. (13625) **
Backup complete. (3740)
proenv>probkup sports2000 test.back1 ?com (Now this one was done with compression. But without the ?scan option. Notice its report of media required **).
OpenEdge Release 10.2B as of Mon Dec 14 17:02:01 EST 2009
NOTE: Backup media estimates done without database scan. (6678) **
Estimate for uncompressed full backup is provided. (6680) **
Use scan option to allow more accurate estimate. (6685) **
1347 active blocks out of 1651 blocks in sports2000 will be dumped. (6686)
0 BI blocks will be dumped. (6688)
The block size is 4096. (6994)
Backup requires an estimated 5.4 MBytes of media. (9285) **
Restore would require an estimated 1347 db blocks using 5.3 MBytes of media. (9286)
Backed up 1347 db blocks in 00:00:00 **
Wrote a total of 19 backup blocks using 2.5 MBytes of media. (13625) **
Backup complete. (3740)
proenv>probkup sports2000 test.back2 -com ?scan (This backup made use of the ?scan option. See the difference in media requirements. **)
OpenEdge Release 10.2B as of Mon Dec 14 17:02:01 EST 2009
1340 active blocks out of 1651 blocks in sports2000 will be dumped. (6686) **
0 BI blocks will be dumped. (6688)
The block size is 4096. (6994)
Backup requires an estimated 2.4 MBytes of media. (9285) **
Restore would require an estimated 1340 db blocks using 5.2 MBytes of media. (9286)
Backed up 1347 db blocks in 00:00:00
Wrote a total of 19 backup blocks using 2.5 MBytes of media. (13625) **
Backup complete. (3740)
Directory listing of the backup files shows the following:
proenv>dir test.back*
Directory of C:\OpenEdge\WRK10.2B
11/30/2010 09:25 AM 5,577,728 test.back (without compression)
11/30/2010 09:25 AM 2,653,184 test.back1 (with compression)
11/30/2010 09:25 AM 2,653,184 test.back2 (with compression and ?scan option ? which really only changes the estimate of media needed for the backup when the command is being issued. It does not change the size of the backup as compression is still being used).
Conclusion: The backup is being compressed because you are making use of the ?com parameter. The estimates for media required when making use of the ?com parameter are not accurate unless you are making use of the ?scan parameter as well.