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Thread: WAL logs and segment files

WAL logs and segment files

From
Eduardo Leva
Date:
Hi, guys... I'm reading the version 7.3.4 documentation and I found this: "
"WAL logs are stored in the directory $PGDATA/pg_xlog, as a set of segment
 files, each 16 MB in size. Each segment is divided into 8 kB pages. The
 log record headers are described in access/xlog.h; record content is
 dependent on the type of event that is being logged. Segment files are
 given ever-increasing numbers as names, starting at 0000000000000000. The
 numbers do not wrap, at present, but it should take a very long time to
 exhaust the available stock of numbers. "
in item 12.2 Implementation. The question is: How do I solve this situation, the remarked situation? The answer is not in the docs. Thanks.

Pd. Sorry about my poor english. I speak spanish every day of my 3rd. world's life...
Sigan adelante... Saludos.

Eduardo Leva
Programador
Santa Fe Argentina.

Re: WAL logs and segment files

From
Bruce Momjian
Date:
Eduardo Leva wrote:
> Hi, guys... I'm reading the version 7.3.4 documentation and I found this: "
>
> "WAL logs are stored in the directory $PGDATA/pg_xlog, as a set of segment
>  files, each 16 MB in size. Each segment is divided into 8 kB pages. The
>  log record headers are described in access/xlog.h; record content is
>  dependent on the type of event that is being logged. Segment files are
>  given ever-increasing numbers as names, starting at 0000000000000000. The
>  numbers do not wrap, at present, but it should take a very long time to
>  exhaust the available stock of numbers. "
>
> in item 12.2 Implementation. The question is: How do I solve this
> situation, the remarked situation? The answer is not in the docs. Thanks.

What situation do you need to solve?  The wrapping?  The documention
states "a very long time", but it more of a joke.  That number would be
huge to wrap around and you would be updating your PostgreSQL version
long before it would ever wrap.

The number is actually an int8 that has a maximum value of:

    18446744073709551616

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

Re: WAL logs and segment files

From
kaolin fire
Date:
If you know where I can get a 1.5e+11 terabyte drive, I'd love to hear
it. ;)

-kaolin fire
-http://erif.org/code/fallingup/

On Feb 20, 2004, at 12:29 PM, Bruce Momjian wrote:

> Eduardo Leva wrote:
>> Hi, guys... I'm reading the version 7.3.4 documentation and I found
>> this: "
>>
>> "WAL logs are stored in the directory $PGDATA/pg_xlog, as a set of
>> segment
>>  files, each 16 MB in size. Each segment is divided into 8 kB pages.
>> The
>>  log record headers are described in access/xlog.h; record content is
>>  dependent on the type of event that is being logged. Segment files
>> are
>>  given ever-increasing numbers as names, starting at
>> 0000000000000000. The
>>  numbers do not wrap, at present, but it should take a very long time
>> to
>>  exhaust the available stock of numbers. "
>>
>> in item 12.2 Implementation. The question is: How do I solve this
>> situation, the remarked situation? The answer is not in the docs.
>> Thanks.
>
> What situation do you need to solve?  The wrapping?  The documention
> states "a very long time", but it more of a joke.  That number would be
> huge to wrap around and you would be updating your PostgreSQL version
> long before it would ever wrap.
>
> The number is actually an int8 that has a maximum value of:
>
>     18446744073709551616
>
> --
>   Bruce Momjian                        |  http://candle.pha.pa.us
>   pgman@candle.pha.pa.us               |  (610) 359-1001
>   +  If your life is a hard drive,     |  13 Roberts Road
>   +  Christ can be your backup.        |  Newtown Square, Pennsylvania
> 19073
>
> ---------------------------(end of
> broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if
> your
>       joining column's datatypes do not match

Re: WAL logs and segment files

From
"scott"
Date:
Take me off your list! You have the wrong scott!
----- Original Message -----
From: "Bruce Momjian" <pgman@candle.pha.pa.us>
To: "Eduardo Leva" <eeeggg499@netscape.net>
Cc: <pgsql-admin@postgresql.org>
Sent: Friday, February 20, 2004 12:29 PM
Subject: Re: [ADMIN] WAL logs and segment files


> Eduardo Leva wrote:
> > Hi, guys... I'm reading the version 7.3.4 documentation and I found
this: "
> >
> > "WAL logs are stored in the directory $PGDATA/pg_xlog, as a set of
segment
> >  files, each 16 MB in size. Each segment is divided into 8 kB pages. The
> >  log record headers are described in access/xlog.h; record content is
> >  dependent on the type of event that is being logged. Segment files are
> >  given ever-increasing numbers as names, starting at 0000000000000000.
The
> >  numbers do not wrap, at present, but it should take a very long time to
> >  exhaust the available stock of numbers. "
> >
> > in item 12.2 Implementation. The question is: How do I solve this
> > situation, the remarked situation? The answer is not in the docs.
Thanks.
>
> What situation do you need to solve?  The wrapping?  The documention
> states "a very long time", but it more of a joke.  That number would be
> huge to wrap around and you would be updating your PostgreSQL version
> long before it would ever wrap.
>
> The number is actually an int8 that has a maximum value of:
>
> 18446744073709551616
>
> --
>   Bruce Momjian                        |  http://candle.pha.pa.us
>   pgman@candle.pha.pa.us               |  (610) 359-1001
>   +  If your life is a hard drive,     |  13 Roberts Road
>   +  Christ can be your backup.        |  Newtown Square, Pennsylvania
19073
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
>       joining column's datatypes do not match