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how_to:database_issues [2010/10/07 12:27] paulhow_to:database_issues [2018/11/14 10:45] (current) – external edit 127.0.0.1
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 ======Database Issues====== ======Database Issues======
  
-VPOP3 version 3 and later use the [[http://www.postgresql.org|PostgreSQL]]] database server. This is an open source enterprise level database server. Several VPOP3 problems are due to problems with the database.+VPOP3 version 3 and later use the [[http://www.postgresql.org|PostgreSQL]]] database server. This is an open source enterprise level database server. Several VPOP3 problems are due to problems with the database service.
  
-=====Disk Caching===== +  * [[Database & Disk Caching]] 
- +  [[Software conflicting with database]] 
-One key point is that, like all other high-end databases, PostgreSQL should not be run on a server with disk level [[http://en.wikipedia.org/wiki/Cache#Operation|write back caching]]. With write back caching, the disk will report data as being written to disk when it is still in the disk's cache memory. If the power then fails, this data is lost and can cause database corruption. As long as the database server really knows when the data has been written to disk, power failure will not cause database corruption as it can be automatically recovered after a power failure. +  * [[VPOP3DB/PostgreSQL service not starting|VPOP3DB Service not starting]] 
- +  * [[Database Size]]
-High-end RAID controllers often contain a battery backed write cache (BBWC) - in this case, if the power fails, the cached data is held in battery powered memory until the power is restored. After power is restored the cached data will be written to disk. In this case, using write back caching through the BBWC is perfectly safe (as long as power is not left off for so long that the batteries run down). +
- +
-It is slightly less safe, but still usually OK, to have a UPS with automated shutdown of the PC. You still have to ensure that the PC is not just turned off without shutting down properly. +
- +
-If you don't have either of these facilities, then make sure you turn off write-back caching in Windows. +
- +
-Exactly how you turn off write-back caching depends on your version of Windows, and the disk controller. +
- +
-The instructions below are for Windows 7 with standard SATA disks +
- +
-  - Go to the 'Device Manager' in Windows. In Windows 7 this is via **Control Panel -> System -> Device Manager**\\ {{:how_to:device_manager.png|}} +
-  - Under **Disk Drives** find the hard disk that VPOP3 is installed on, and right-click it and choose **Properties**\\ {{:how_to:disk_properties.png|}} +
-  - Go to the **Policies** tab. Turn off **Enable write caching onthe device** and press **OK**\\ {{:how_to:write_caching.png|}} +
- +
-=====Possible Conflicting Software===== +
-We strongly recommend that virus scanners exclude the VPOP3\pgsql\data folder and all subfolders. If a virus scanner decides to quarantine a file from within this folder structure, that can cause VPOP3 not to run, and could lead to data loss or corruption. +
- +
-We also recommend that backup software does not backup this folder structure. If a backup program opens a file for backup, and then the database server needs it, it can cause problems, and crashes.+
  
 =====Database corruption===== =====Database corruption=====
-If VPOP3 won't start even though the process is running, then that is often because the PostgreSQL service is not running. If the PostgreSQL service won't start, or keeps crashing, then it is probably because the database is corrupted.+If VPOP3 won't start even though the process is running, then that is often because the PostgreSQL service is not running. If the PostgreSQL service won't start, or keeps crashing, then it is probably because the database is corrupted. In VPOP3 versions 3 and 4, the PostgreSQL service is usually called 'Postgres-VPOP3'. In version 5 and later, the service is called 'VPOP3DB'
  
   * [[Restore a database backup|Restoring a database]]   * [[Restore a database backup|Restoring a database]]
-  * [[PostgreSQL server won't start due to damaged log files]]+  * [[PostgreSQL server won't start due to damaged log files]] or missing pg_control file
   * [[Total Rebuild of Database]]   * [[Total Rebuild of Database]]
 +  * [[Repairing corrupted database]]
  
-=====PostgreSQL service not starting===== +Our chargeable support service will be able to help with this if necessaryNote that we cannot guarantee recovering dataas that will depend on how badly the database has been damaged, and when the latest good backup was.
-If the PostgreSQL service doesn't start, or starts and immediately stops, there are a couple of things you can do: +
- +
-  * Look in the VPOP3\pgsql\data\pg_log folder for a log file created at the time when you started VPOP3If that is thereyou can read that (using Notepad) and see if it reports any problems with files or 'relations'. If so, it might be a problem with a damaged database +
-  * Look in the Windows event log for entries relating to PostgreSQL +
- +
-You can also try starting the PostgreSQL service manually: +
- +
-From a command promptrun "runas /user:postgres cmd" (password is "vla8Pi4cluwrouDiERiU"+
- +
-Then  +
-  c: +
-  cd \vpop3\pgsql\bin +
-  pg_ctl -D "C:\vpop3\pgsql\data" start  +
-   +
-(If your VPOP3 is installed in a different directory, change the above paths as appropriate) +
- +
-See what response you get to the pg_ctl command +
  
how_to/database_issues.1286454463.txt.gz · Last modified: 2018/11/14 10:44 (external edit)