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Video : Scalable Sequences in Oracle Database 18c Onward

In today’s video we’ll discuss Scalable Sequences, which were documented for the first time in Oracle 18c.

The video is based on this article.

The star of today’s video is David Peak, who is now working on the Oracle Pandemic Response Systems. This video is a throwback to a hotel we stayed in at São Paulo a few years back.

Cheers

Tim…

Join Performance for UUID, STRING, and INTEGER with CockroachDB

overview

To continue on the UUID performance thread, I was recently asked by a customer how joins perform with various data types. I had not run a specific test, but suspected perform would be driven mostly by the size of the data types.

I wanted to verify my assumptions with real test data that shows the core performance of joins with CockroachDB.

the schema, data, and queries

For this test, two tables were created. The first table had one million rows and the second table had 200k matching primary keys for UUID, STRING, and INTEGER data types.

schema:

create table u1 (id uuid primary key);
create table u2 (id uuid primary key);

create table s1 (id string primary key);
create table s2 (id string primary key);

create table i1 (id integer primary key);
create table i2 (id integer primary key);

data load:

Direct Path

This is a little addendum to a note I wrote a couple of days ago about serial direct path reads and KO (fast object checkpoint) enqueue waits.

The original note was prompted by a problem where someone had set the hidden parameter “_serial_direct_read” to ‘always’ because there were running 11g and wanted some “insert as select” statements to use direct path reads on the select portion and 11g wasn’t co-operating.

Serial direct path reads were introduced as a possibility in (at least) the 8.1.7.4 timeline, but the parameter was set to false until 11gR2 where it changed to auto. (Legal values are: false, true, never, auto, always.)

Direct Path

Here’s a note that I might have written once already – but I can’t find it and I’ve just been reminded about what it (might have) said by a posting that came up on the Oracle database forum in the last few days.

The posting in question is asking why, after setting the hidden parameter _serial_direct_read to ‘always’ a particular query is now taking hours to complete when it used to complete in a minute or so.

Video : Multitenant : Disk I/O (IOPS, MBPS) Resource Management for Pluggable Databases (PDBs)

In today’s video we’ll discuss how Resource Manager allows us to manage the disk I/O (IOPS, MBPS) usage in PDBs. This can be useful to stop a small number of PDBs using all disk IOPS and/or bandwidth on the server.

The video is based on the following article.

You might also find these useful.

Serial Bloom

Following the recent note I wrote about an enhancement to the optimizer’s use of Bloom filters, I received a question by email asking about the use of Bloom filters in serial execution plans:

I’m having difficulty understanding the point of a Bloom filter when used in conjunction with a hash join where everything happens within the same process.

I believe you mentioned in your book (Cost Based Oracle) that hash joins have a mechanism similar to a Bloom filter where a row from the probe table is checked against a bitmap, where each hash table bucket is indicated by a single bit. (You have a picture on page 327 of the hash join and bitmap, etc).

Video : Multitenant : Memory Resource Management for Pluggable Databases (PDBs)

In today’s video we’ll discuss how Resource Manager allows us to manage the memory usage in PDBs. This can be useful to stop a small number of PDBs using all memory assigned to the instance.

This video was based on this article.

You might also find these useful.

Video : Multitenant : Dynamic CPU Scaling – Resource Manager Control of CPU using CPU_COUNT and CPU_MIN_COUNT

In today’s video we’ll discuss how Resource Manager can control CPU usage in PDBs using the CPU_COUNT and CPU_MIN_COUNT parameters. Oracle call this Dynamic CPU Scaling. This can be useful to stop a small number of PDBs using all CPU resources assigned to the instance.

This video is based on the following article.

Video : Instance Caging to Manage CPU Usage

In today’s video we’ll discuss instance caging to manage CPU usage. This can be useful when we are trying to consolidate multiple instances on a single server.

This video is based on the following article.

The star of today’s video is the beard belonging to Victor Torres. I feel totally inadequate with my patchy stubble… </p />
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