Rogerio Eguchi Blog

OCI – Oracle Cloud Agent Commands

Oracle Cloud Agent Commands is another useful feature recently launched on OCI.

This resource gives you the ability of remotely running scripts within the instance using the run command feature.

Let’s say you need to restart the sshd deamon to be able to login again.

Not a problem, just go to the console, hit create command and write a script to start it up again 🙂

After a few minutes you can check the output:

Return code was sucessfull but it actually failed with error below:

Failed to start sshd.service: Interactive authentication required.
See system logs and 'systemctl status sshd.service' for details.
Mon Dec 14 21:21:05 GMT 2020

For privileged commands to work you need to grant sudo privileges to ocarun user.

You can also check the logs at /var/log/oracle-cloud-agent/plugins/runcommand/runcommand.log file.

IAM policies are required for this feature to work so go ahead and read the documentation here.

AWS – EBS gp3

AWS announced the general availability of EBS gp3 which is 20% cheaper then gp2 and allows you to provision performance (IOPS and throughput) independent of storage capacity.

Baseline performance on a 1Tb gp2 volume is 3000 IOPS and 250 mb/s throughput.

Baseline performance on gp3 is 3000 IOPS and 125mb/s throughput, regardless of volume size.

Provisioning gp3 performance will cost you a fee.

Example:

Detailed pricing information available at https://aws.amazon.com/ebs/pricing/

So, from now on, instead of using gp2, just go with gp3 and use more disks so you can reach the same throughput as gp2 and save a few (or a lot) of money.

Check the instance type volume limits here so you can better understand how many volumes you need to reach instance max performance.

We have started moving some volumes from gp2 to gp3 and seeing some disk latency increase so I recommend you doing it on most idle periods.

Variable substitution using new_val

This is not new but I wasn’t aware of this cool feature !

You can assign a value to a variable using new_val on SQLPlus.

From the doc: “Specifies a variable to hold a column value”

Example:

column PROPERTY_VALUE new_val temporary_tablespace

select PROPERTY_VALUE from database_properties where PROPERTY_NAME = 'DEFAULT_TEMP_TABLESPACE';

This way I can easily assign the output from the select command to the variable temporary_tablespace.

You can check the variable’s value using define command:

define temporary_tablespace

Easy, right ?

OCI – ExaCS provisioning bug

If you are about to launch an ExaCS using the new resource model be aware of BUG 32104352 – Provisioning fails with minimum value for vcpu count is 4.

You should be able to launch an ExaCS with only one ocpu in each node but it will fail to provision due to this bug.

Fix is very simple, you just need to define a value of 4 or above for the OCPU.

After provisioning is completed, you can scale up/down the OCPU’s online.

Happy provisioning 🙂

Faster ASM Rebalance

Yes, it is possible to accomplish it but only if you have a flash storage.

Why ?

Because in this case you can skip the Compact Phase of ASM rebalance operation.

For 12c onwards, you can use the command below to skip the compact phase:

ALTER DISKGROUP <DG_NAME> SET ATTRIBUTE '_rebalance_compact'='FALSE';

But before running this command, please read the following articles so you can better understand what you are doing.

Rebalancing act – http://asmsupportguy.blogspot.com/2011/11/rebalancing-act.html

MOS Note 1902001.1 – What is ASM rebalance compact Phase and how it can be disabled

ASM Rebalance Too Slow? 3 Tips To Improve Rebalance Times – https://flashdba.com/2015/04/17/asm-rebalance-too-slow-3-tips-to-improve-rebalance-times/

Statspack batch install

If you don’t have Oracle Diagnostics pack or is running Oracle Standard Edition, just go for statspack !

In this blog post I will show you how to install it in batch mode.

It is actually very simple, you just need to define three variables:

connect / as sysdba

define default_tablespace='perfstat'
define temporary_tablespace='temp01'
define perfstat_password='YourComplexStatspackPassword'

then run

@?/rdbms/admin/spcreate.sql

Simple, isn’t ?

I would also recommend you to take a look at Franck’s way of improving statspack here.

OCI – iSCSI bug 30711156

If you run Oracle DB on OCI compute and leverage iSCSI as volume attachment, beware of bug 30711156 on iSCSI.

We hit this bug a while ago and as consequence we were not able to read/write to the block volume anymore.

Fix: kill all Oracle processes then remount the Filesystem.

If you see errors on /var/log/messages like the ones below, you mostly like hit the same issue:

Aug 10 00:29:30 host iscsid: iscsid: Kernel reported iSCSI connection 1:0 error (1020 - ISCSI_ERR_TCP_CONN_CLOSE: TCP connection closed) state (3) 
Aug 10 00:29:30 host iscsid: iscsid: re-opening session 1 (reopen_cnt 0) 
Aug 10 00:29:30 host iscsid: iscsid: disconnecting conn 0x563c2f155068, fd 7 
Aug 10 00:33:01 host kernel: session1: iscsi_eh_cmd_timed_out scsi cmd ffff9c3622aea948 timedout 
Aug 10 00:33:01 host kernel: session2: iscsi_eh_cmd_timed_out scsi cmd ffff9c3622ae8d48 timedout 
Aug 10 00:33:01 host kernel: session1: iscsi_eh_cmd_timed_out return timer reset 
Aug 10 00:33:01 host kernel: session2: iscsi_eh_cmd_timed_out return shutdown or nh 
Aug 10 00:33:01 host kernel: session1: iscsi_eh_cmd_timed_out scsi cmd ffff9c3622aec148 timedout 
Aug 10 00:33:01 host kernel: session1: iscsi_eh_cmd_timed_out return timer reset

Nice, right ?

A new iscsi-initiator-utils is available for download so go ahead and update your server.

Linux Errata available here.

Good patching !

AWS cli for rds reports

Another quick blog post on AWS stuff.

You can query your RDS metadata information using aws cli.

This is a very useful approach when you manage hundreds of servers and need to build a report.

Here is the command line I’ve got to retrieve the database name, license model, DB engine and DB version.

aws rds describe-db-instances --region us-east-1 --query "*[].{DBInstanceIdentifier:DBInstanceIdentifier,LicenseModel:LicenseModel,Engine:Engine,EngineVersion:EngineVersion}" --output table

You can find other rds cli options here.

AWS Nitro – volume id and device name

Hi all,

Quick blog post about EBS on AWS nitro instances.

When working with AWS Nitro instances your EBS volumes will be exposed as NVMe block devices, i.e nvme0n1/nvme1n1, etc, regardless what your input is when provisioning them.

But you can use the nvme tool to map the NVMe device name to the actual name you have provided:

[ec2-user ~]$ sudo nvme id-ctrl -v /dev/nvme1n1
NVME Identify Controller:
vid : 0x1d0f
ssvid : 0x1d0f
sn : vol01234567890abcdef
mn : Amazon Elastic Block Store
…
0000: 2f 64 65 76 2f 73 64 6a 20 20 20 20 20 20 20 20 "/dev/sdf…"

So in this case I’ve used sdf as block volume name and ended up with nvme1n1 on my instance.

I highly recommend you to read the docs here and watch a cool video.

OCI CLI authentication for federated users

In this short blog post I will explain how to authenticate using a federated user instead of a local one.

Install your oci cli then run:

oci session authenticate

Inform the region your tenant is subscribed to, login to the console and define profile name that better suits you.

A config file will be saved on your computer.

You can test your access running:

oci iam region list --config-file <config> --profile <name> --auth security_token

The default token TTL is set to 1 hour before it expires and can be refreshed within the validity period up to 24 hours. To refresh the token run:

oci session refresh --profile <name>

Hope it helps !