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VPOP3 version 3 and later use the PostgreSQL] database server. This is an open source enterprise level database server. Several VPOP3 problems are due to problems with the database service.
One key point is that, like all other high-end databases, PostgreSQL should not be run on a server with disk level 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.
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. (Note that 'Server' versions of Windows will usually have write-back caching disabled by default, because they often store critical data and run database servers, and 'Desktop' versions of Windows will usually have write-back caching enabled by default, because their data is usually less critical, and speed is considered more important than reliability).
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
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.
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'
Our chargeable support service will be able to help with this if necessary. Note that we cannot guarantee recovering data, as 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:
You can also try starting the PostgreSQL service manually:
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
In the Windows Event Viewer, view the Application event log, then look for Error entries for the PostgreSQL source.
Depending on your installation, the events may all be displayed as something like:
The description for Event ID xxxx from source PostgreSQL cannot be found. Either the component that raises this event is not installed on your local computer....
If that's the case, don't worry, just look lower down in the event message. It will say something like
The following information was included with the event
It is that information you need to see. Some possible event messages we have seen are:
If this is the case, then usually it means that a previous attempt to start PostgreSQL was made, but it timed out or something, and is now in a 'partially' running state.
To solve this, go to Windows TaskManager (Ctrl-Alt-Del - choose TaskManager), then go to the Processes tab and click Show processes for all users. Sort by Image Name, and End Process on all the postgres.exe processes. Once those are all ended, then you should be able to start the VPOP3DB service manually.
If you get FATAL or PANIC entries in the PostgreSQL log files (in VPOP3\pgsql\data\pg_log) then they may give more information about why PostgreSQL could not start. Some log entries we have come across are below.
This usually happens if the PC where VPOP3 is installed used to only have IPv4 installed, and has now had IPv6 added. The PostgreSQL configuration needs altering to support IPv6.
Usually this only happens on Windows XP - earlier versions of Windows do not support IPv6, and later versions support IPv6 by default. Windows XP needs to have IPv6 manually installed
To fix this problem, go to the VPOP3\pgsql\data folder on the server and edit the pg_hba.conf file using a plain text editor such as Notepad.
Near the bottom of that file you should see a section saying
# TYPE DATABASE USER CIDR-ADDRESS METHOD # IPv4 local connections: host all all 127.0.0.1/32 md5 # IPv6 local connections: #host all all ::1/128 md5
Edit the last line to remove the # from the start, so it now says
# TYPE DATABASE USER CIDR-ADDRESS METHOD # IPv4 local connections: host all all 127.0.0.1/32 md5 # IPv6 local connections: host all all ::1/128 md5
In some cases the last two lines may not exist, in which case you can simply copy those lines from the example above and paste them into your pg_hba.conf file
You will then need to restart the PostgreSQL service in Windows. Note that sometimes PostgreSQL cannot close down properly, and there will be unwanted 'postgres.exe' processes visible in Windows TaskManager on the Processes tab. If so, then end those processes manually, before restarting the service.