Re: Help implementing Public RBS

The number of rollback segments grabbed by any instance is determined by dividing the transactions parameter by the transactions_per_rollback_segment parameter.

From the docs
By default, when an instance starts, it acquires TRANSACTIONS/TRANSACTIONS_PER_ROLLBACK_SEGMENT rollback segments. If you want to ensure that the instance acquires particular rollback segments that have particular sizes or particular tablespaces, specify the rollback segments by name in the ROLLBACK_SEGMENTS parameter in the instance's parameter file.

From the Oracle Server Administrators Guide:

How Instances Acquire Rollback Segments When an instance starts up, it uses the TRANSACTIONS and TRANSACTIONS_PER_ROLLBACK initialization parameters to determine how many rollback segments to acquire, as follows:  This total_rollback_segments_required number is rounded up.

At startup, an instance attempts to acquire rollback segments as follows.

From the Oracle Parallel Server Guide:

An instance first acquires any private rollback segments specified by the ROLLBACK_SEGMENTS initialization parameter. If this total_private_rollback_segments number is more than the total_rollback_segments_required, then no further action is taken to acquire rollback segments.
If no private rollback segments are specified in the initialization file, the instance attempts to acquire public rollback segments. If the total_private_rollback_segments falls short of the total_rollback_segments_required, then the instance attempts to make up the difference by acquiring public rollback segments. If only one private rollback segment is specified and acquired, or one public rollback segment is acquired, the instance will start up, even if one rollback segment is below the total_rollback_segments_ required, in which case Oracle generates a message.
If a private rollback segment cannot be brought online at instance startup, the startup fails and Oracle generates a message. Note: The total number of rollback segments in a parallel server cannot be greater than the value of the initialization parameter GC_ROLLBACK_SEGMENTS. If an instance tries to acquire more rollback segments than this parameter allows, Oracle generates a message and the instance will not start up. See Also: "Monitoring Rollback Segments" .

Assuming you all read and understood this, did you check the transactions and transactions_per_rollback_segments parameter. Default values are often quite high.

IMO, You'll definitely need more rollback segments. Five public only should be insufficient.

Hth,
Sybrand Bakker, Oracle DBA

Sidhe <sidhe_at_home.net> wrote in message news:38EB63D5.1E4B5104_at_home.net...
> Oracle support has been absolutely no help on this and the documentation
> leaves much to be desired.
>
> We're running Oracle 7.3.4.2 on AIX 4.3.2.
>
> I'm trying to create several PUBLIC rollback segments to be used by my 3
> instances. Here's what I did...
>
> Dropped all current RBS's in all instances
> Deleted all current Rollback Tablespaces in all instances
> Created new Rollback Tablespace in PROD instance
> Created 5 new PUBLIC RBS's in PROD instance
> Removed RBS parameter in INIT.ORA files for all instances
> Bounced all instances
>
> Here's what happened...
>
> The PROD instance with the 5 new public RBS's came up with only 2 of the
> 5 in an online status
> (remember I REMOVED the RBS parms in the INIT.ORA's)
> The DEV and TEST instances came up fine but blow up trying to use the
> system RBS
> (it's like they don't know about the public RBS's)
>
> Furthermore...
> I've tried putting the RBS parameter back in the INIT.ORA but that only
> allows PROD to come up with all 5 RBS's online and DEV and TEST won't
> even start because they claim I'm referencing RBS's which do not exist.
>
> So my question is... what am I doing wrong? What is the correct method
> of implementing PUBLIC Rollback Segments?
>
> Thanks in advance,
> Roger Westbrook DBA/Sys Admin
> Dollar General Corp
> rwestbrook_at_dollargeneral.com
>
Received on Wed Apr 05 2000 - 11:25:16 CDT