I like to use the linux utility sar (system activity reporter (?)) I gives a fast and quite complete overview over the performance of a linux system. SAR has a lot of possibilitys. I just highlight a few of them to remember how the syntax is 🙂 CPU information of today oracle@lqas4342:~$sar Linux 4.18.0-425.13.1.el8_7.x86_64 (lqas4342.mod.nl) …
Just a reminder I keep forgetting what the environment variable is called: ORA_ASKENV ORA_ENVASK ORAASK_ENV ORAENV_ASK This is _the_ variable: ORAENV_ASK=NO ORAENV_ASK=YES Happy scripting
Just a write up of the filters I sometimes use/need. (work in progress…) Filtering _out_ ssh: tcpdump “port ! ssh” Just seeing ICMP packets: tcpdump “icmp” Filtering on port _and_ host: tcpdump “port ssh && host host-name”
When installing security/kernel packages the system must be rebooted. It would be a bit silly to reboot always. So..without further ado…you can solve this for example with the following playbook: [martijn@fedora basis]$ cat update_all.yaml — – name: Update alle hosts hosts: all become: true tasks: – name: install dnf tools dnf: state: present name: dnf-utils …
Index Why In the DB2 : Cost Calculation 2 : index only post I noticed something upsetting, well, at least it was upsetting to me. We looked at the explain plan for looking up 1 value by an index. The index had nlevel=3. So there is a root-node, some intermediate-nodes and finally finally some leaf-nodes. …
I started a series of articles concerning the cost of queries (and as a consequence concerning the choices the optimizer makes). This post is a index of these articles. 1 – DB2 : Cost calculations 1 : Table Scan 2 – DB2 : Cost Calculations 2 : Index Only 3 – DB2 : Cost Calculations …
Index Why indexes Searching through millions of rows can be the right thing to do (TBSCAN). It might be the only option available to get the data you need.But in a lot of cases we need smarter ways to get to our data. If you need only one row,it seems silly to process thousands of …
Index Why? When you supply DB2 with a query DB2 has to make some serious decisions: – Should indexes be utilized? – Which indexes are most suitable? – Which join operation should be used? (hash join/nested loop) – Is all data needed at once or are the first 10 rows as quick as possible (the …
Just a quick reminder: If you start a new database where you want to genrate some execution-plans you might run into the following : db2 => explain plan for select * from t1,t3 where t1.n1=t3.n1; DB21034E The command was processed as an SQL statement because it was not a valid Command Line Processor command. During …
Sometimes you need a mechanism to generate rows. For example when you need to create a demonstration table . Recursive CTE’s (Common Table Expression) might be your friend WITH engine (rownum) AS (select 1 as rownum from sysibm.sysdummy1 union all select rownum + 1 AS rownum from engine where rownum<10) SELECT rownum FROM engine; …