Rollback Segment Online at Instance Startup

[Sharma]

What I know, Oracle at Instance startup decides No. of Rollback segments to bring online on either of the two settings

ROLLBACK_SEGMENTS=(RBS01,...RBS0n)
or
transactions=40
transactions_per_rollback_segment=8

transactions / transactions_per_rollback_segment

I have the parameter ROLLBACK_SEGMENTS commented out thinking the transactions / transactions_per_rollback_segment
will bring atleast 5 RBS online.
But this is not happening, Why?
What are Oracle's intention on implementing this new way of automatically bringing the RBS online based on transactions / transactions_per_rollback_segment.

Please Clarify.

[Shestakov]

If u have to use :
transactions=40
transactions_per_rollback_segment=8

u should have PUBLIC rollback segments in database.
These parameters will not activate usual (NOT PUBLIC) rollback segments.

Oracle use parameters:
transactions
transactions_per_rollback_segment
for make decision "how many PUBLIC rbs have to online after startup.

If u have only usual (NOT PUBLIC) rollback segments, then u must
write parameter:
ROLLBACK_SEGMENTS=(....)

[Edited by Shestakov on 05-24-2002 at 01:58 PM]

[Sharma]

Any reason why Oracle adopted this strategy of bringing them online automatically without specifying then in parameter, ROLLBACK_SEGMENTS=()

[clio_usa]

But this is not happening, Why?
What are Oracle's intention on implementing this new way of automatically bringing the RBS online based on transactions / transactions_per_rollback_segment.

Sharma,

Unless you specify the RBS names in ROLLBACK_SEGMENTS parameter, HOW does Oracle knows how you named your rollback segments, or do you have any ??????

Here is what those parameters are created for:

TRANSACTIONS_PER_ROLLBACK_SEGMENT specifies the number of concurrent transactions you expect each rollback segment to have to handle. The minimum number of rollback segments acquired at startup is TRANSACTIONS divided by the value for this parameter.

TRANSACTIONS specifies the maximum number of concurrent transactions. Greater values increase the size of the SGA and can increase the number of rollback segments allocated.

and

ROLLBACK_SEGMENTS allocates one or more rollback segments by name to this instance.

If you specify only TRANSACTIONS and TRANSACTIONS_PER_ROLLBACK_SEGMENT , then no private RBS would be allocated and public RBS will be used if you have any. In your case you don't have any, and that is why

But this is not happening

Unless, you create private RBS and specify them in ROLLBACK_SEGMENTS, or create public RBS, you will not have RBS allocated.

That might lead you to error like THIS ONE

Hope that helps,



clio_usa
OCP 8, 8i, 9i - Senior Oracle DBA
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