Re:Could not read from file "pg_subtrans/00F5" at offset 122880: Success.

On 11/27/23 03:50, Sri Mrudula Attili wrote:

Hello,

Post refresh of a Delphix VDB , while trying to connect from application
users are getting the below error.

Could also see these errors in postgresql.log

Error Message:

< 2023-11-24 12:24:10.031 GMT >ERROR:  could not access status of
transaction 16087052
< 2023-11-24 12:24:10.031 GMT >DETAIL:  Could not read from file
*"pg_subtrans/00F5" at offset 122880: Success.*
< 2023-11-24 12:24:10.031 GMT >STATEMENT:  SELECT distinct

Postgresql Version:

----------------------------------------------------------------------------------------------------------
 PostgreSQL 11.16 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5
20150623 (Red Hat 4.8.5-44), 64-bit

From this:

https://docs.delphix.com/docs537/delphix-administration/postgresql-environments-and-data-sources/provisioning-vdbs-from-postgresql-dsources/provisioning-a-postgresql-vdb

there seems to be a lot of moving parts to using Delphix VDB with a
Postgres database. You are going to need to provide more information
about your setup.

Thanks,

Sri Attili

--
Adrian Klaver
adrian.klaver@aklaver.com

On Mon, 2023-11-27 at 11:50 +0000, Sri Mrudula Attili wrote:

ERROR:  could not access status of transaction 16087052
DETAIL:  Could not read from file "pg_subtrans/00F5" at offset 122880: Success.
STATEMENT:  SELECT distinct 

That's data corruption.
Time to restore your backup.

Investigate how you got there. Did you run "pg_resetwal"?
Did you restore a database from a file system backup?
Did you remove a "backup_label" file? Is your hardware broken?

Yours,
Laurenz Albe

At Mon, 27 Nov 2023 19:58:13 +0100, Laurenz Albe <laurenz.albe@cybertec.at> wrote in

On Mon, 2023-11-27 at 11:50 +0000, Sri Mrudula Attili wrote:

ERROR:  could not access status of transaction 16087052
DETAIL:  Could not read from file "pg_subtrans/00F5" at offset 122880: Success.

By the way, just out of curiosity, but errno should not be zero at the
time the message above was output, yet "%m" is showing "success",
which implies errno = 0 in Linux. How can that happen?

slru.c:961

case SLRU_READ_FAILED:
if (errno)
ereport(ERROR,
(errcode_for_file_access(),
errmsg("could not access status of transaction %u", xid),
errdetail("Could not read from file \"%s\" at offset %d: %m.",

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center

Hello,

Post refresh of a Delphix VDB , while trying to connect from application
users are getting the below error.

Could also see these errors in postgresql.log

Error Message:

< 2023-11-24 12:24:10.031 GMT >ERROR:  could not access status of
transaction 16087052
< 2023-11-24 12:24:10.031 GMT >DETAIL:  Could not read from file
*"pg_subtrans/00F5" at offset 122880: Success.*
< 2023-11-24 12:24:10.031 GMT >STATEMENT:  SELECT distinct

Postgresql Version:

----------------------------------------------------------------------------------------------------------
 PostgreSQL 11.16 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5
20150623 (Red Hat 4.8.5-44), 64-bit

Thanks,

Sri Attili

Hello Laurenz,

 Thanks for your response.

This error we are seeing on a delphix Virtual database that was
refreshed using the snapshot of production standalone database.

It keeps the database in pg_start_backup and to take the snapshot.

I did check the dsource(production) database logs and it hasnt got any
error like this.

Thanks,

Sri Attili

On 2023-Nov-28, Kyotaro Horiguchi wrote:

By the way, just out of curiosity, but errno should not be zero at the
time the message above was output, yet "%m" is showing "success",
which implies errno = 0 in Linux. How can that happen?

If the file is exactly of the length given then seek will work, and read
will not set errno but return a length of 0 bytes. So
SlruPhysicalReadPage sets SLRU_READ_FAILED and then in pg11 the %m in
SlruReportIOError expands to "Success".

The code in master is completely different (it uses pg_pread rather than
seek + read): it does test for errno and reports accordingly.

So, nothing to do here.

--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/

On Wed, Nov 29, 2023 at 12:20 PM Sri Mrudula Attili <sri@ebi.ac.uk> wrote:

Hello Laurenz,

Thanks for your response.

This error we are seeing on a delphix Virtual database that was
refreshed using the snapshot of production standalone database.

It keeps the database in pg_start_backup and to take the snapshot.

Isn't pg_basebackup the canonical method for taking a snapshot?
(PgBackRest, too, if you want more speed.)

At Wed, 29 Nov 2023 18:29:15 +0100, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote in

The code in master is completely different (it uses pg_pread rather than
seek + read): it does test for errno and reports accordingly.

So, nothing to do here.

Oops! Thank you and sorry for the noise.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center