HPUX PE size and Oracle PE size

[Sanjiv Sharma_1]

Hi,

rp8400/HP-UX 11.11/Oracle 8i.

I have a volume group which has PE size 8MB and also the Oracle DB has the PE size of 8MB.

Now I have the requirement to change the PE size to 32 MB.

Can we have PE size 32 MB and Oracle PE size 8 MB? Is this configuration supported?
What will be the impact on performance?

Any Advice.
Thanks,

[Massimo Bianchi · Accepted solution]

Hi,
are you sure your oracle db has a db_block_size of 8M ?
Usually on hpux it is 8192 bytes, let's say 8K.

Usually the VG PE size it's of no matter, what is really important for performance is the os block size, the one you set with the -b 8192 of the command newfs.

In a VG you CANNOT mix different PE, so you will have to re-create the VG, but it is fully supported to have different VG with different PE size.In a VG the PE SIZE is fixed at creation time.

HTH,
Massimo

[Radhakrishnan Venkatara]

hi,

one thing if u want ur PE to 32MB u have to recreate the volume group there is no choice.

I don't how they are going to impact.

check this links:

http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x7897abe92dabd5118ff10090279cd0f9,00.html



http://forums.itrc.hp.com/cm/QuestionAnswer/1,,0x6661dfe5920fd5118fef0090279cd0f9,00.html

radhakrishnan

[T G Manikandan]

I think you are talking about the OS BLOCK SIZE and DB_BLOCK_SIZE.

If you are speaking about increasing OS BLOCK SIZE then

Oracle recommends the DB_BLOCK_SIZE to be equal or multiples of OS_BLOCK_SIZE.

If your DB_BLOCK_SIZE is smaller than the OS_BLOCK_SIZE then each read from the OS can only pass less bytes to the database.


Also,once the file system/database is created with a block size you cannot alter it without recreating them.


Thanks

[RolandH]

Hi Manikandan,

I don't think that Orcale recommends the DB_BLOCK_SIZE to be equal or multiples of OS_BLOCK_SIZE. Equal is OK, but the DB_BLOCK_SIZE greater than OS_BLOCK_SIZE seems to be nonsens. I think it is the other way what you mean, beause one OS_BLOCK will be written in one I/O to the disk. If you have a DB_BLOCK_SIZE, which is a double of the OS_BLOCK_SIZE you will have two I/O to the disk that decreases the performance of your system. Or I'm wrong.


Roland

[RolandH]

Hi Manikandan,

I don't think that Orcale recommends the DB_BLOCK_SIZE to be equal or multiples of OS_BLOCK_SIZE. Equal is OK, but the DB_BLOCK_SIZE greater than OS_BLOCK_SIZE seems to be nonsens. I think it is the other way what you mean, beause one OS_BLOCK will be written in one I/O to the disk. If you have a DB_BLOCK_SIZE, which is a double of the OS_BLOCK_SIZE you will have two I/O to the disk that decreases the performance of your system. Or I'm wrong.


Roland

[RolandH]

Hi Manikandan,

I don't think that Orcale recommends the DB_BLOCK_SIZE to be equal or multiples of OS_BLOCK_SIZE. Equal is OK, but the DB_BLOCK_SIZE greater than OS_BLOCK_SIZE seems to be nonsens. I think it is the other way what you mean, beause one OS_BLOCK will be written in one I/O to the disk. If you have a DB_BLOCK_SIZE, which is a double of the OS_BLOCK_SIZE you will have two I/O to the disk that decreases the performance of your system. Or I'm wrong.


Roland

[RolandH]

Hi Manikandan,

I don't think that Orcale recommends the DB_BLOCK_SIZE to be equal or multiples of OS_BLOCK_SIZE. Equal is OK, but the DB_BLOCK_SIZE greater than OS_BLOCK_SIZE seems to be nonsens. I think it is the other way what you mean, beause one OS_BLOCK will be written in one I/O to the disk. If you have a DB_BLOCK_SIZE, which is a double of the OS_BLOCK_SIZE you will have two I/O to the disk that decreases the performance of your system. Or I'm wrong.


Roland

[RolandH]

Hi Manikandan,

I don't think that Orcale recommends the DB_BLOCK_SIZE to be equal or multiples of OS_BLOCK_SIZE. Equal is OK, but the DB_BLOCK_SIZE greater than OS_BLOCK_SIZE seems to be nonsens. I think it is the other way what you mean, beause one OS_BLOCK will be written in one I/O to the disk. If you have a DB_BLOCK_SIZE, which is a double of the OS_BLOCK_SIZE you will have two I/O to the disk that decreases the performance of your system. Or I'm wrong.


Roland