create tempdb in swap space

atapojha · #1 (**permalink**) 11-26-07, 08:23

Hi,

I have to install sybase on AIX tommrow. I am a novice when it comes to sybase and have never done it before. I have been asked to create tempdb on a swap device created for it for performance reason.]

My question is does the installation ask you that on which device you want t configure temdb? In this case I can enter the swap device? and if not then what are the steps involved in creating tempdb on swap device? Do I have to do it after the installation as a seperate process?

Please help

Thanks,

Atap

pdreyer · #2 (**permalink**) 11-26-07, 10:22

No, a small tempdb is created on the master device during install
Do it as a separate process by adding a tempdb device afterwords

trvishi · #3 (**permalink**) 11-26-07, 12:10

Theres a known performance gain if you create the first portion after master in /tmp and the rest in a different filesystem. Also dsync should be off for tempdb devices.

i.e.

If you want a 1g tempdb.

a) 2MB in master (default).
b) 100MB in /tmp
c) 900MB in /mytempdbfs

for b) make sure you touch the file in RUN_SERVER file as /tmp gets whacked out in case of a OS reboot.

atapojha · #4 (**permalink**) 11-26-07, 17:00

Thanks guys,

Please correct me if my process is incorrect

1. From installation create tempdb on the default master device which is /sybase/system
2. Extend tempdb by creating 2 2G devices in /sybase/tempdb
3. Extend tempd by running the alter database commands by allocating space on the two devices
4. drop the device for tempdb in master called /systenm/tempdb

So at the end of this I have my tempdb configured in swap space.

Thanks

trvishi · #5 (**permalink**) 11-26-07, 19:15

tats not what I said. Knowingly or unknowingly you asked the right question. /tmp is totally different from user created filesystems. Please read about /tmp and my post and then post again if u have any questions.

atapojha · #6 (**permalink**) 11-27-07, 23:32

Thanks trvishi,

I just read about tempdb in the performance and tuning guide. I will follow the steps to delete the segments related to tempdb in the master device. I will have to expand tempdb on the ram disk. What do I need to specify in the run startup file so that if the server reboots then the device is created again.

Please advise.

Regards,

Atap

pdreyer · #7 (**permalink**) 11-28-07, 02:10

Quote:

Originally Posted by atapojha

What do I need to specify in the run startup file so that if the server reboots then the device is created again

Quote:

Originally Posted by trvishi

for b) make sure you touch the file in RUN_SERVER file

e.g.
touch /tmp/tempdbdev.dat

trvishi · #8 (**permalink**) 11-28-07, 07:58

Quote:

Originally Posted by atapojha

Thanks trvishi,

I just read about tempdb in the performance and tuning guide. I will follow the steps to delete the segments related to tempdb in the master device. I will have to expand tempdb on the ram disk. What do I need to specify in the run startup file so that if the server reboots then the device is created again.

Please advise.

Regards,

Atap

Also dont drop the segments in the master (The 2MB one created while the server is built). Because, if you had to recover the server without any tempdb devices, the server wont come up.