How to check memory consumption and swapping on a Linux server

The easiest way to check for memory consumption on Linux is in my opinion the "free" utility:

oracle@prodserver1:[proddb01]# free -m
             total       used       free     shared    buffers     cached
Mem:         16056       9027       7029          0        233       1093
-/+ buffers/cache:       7700       8356
Swap:         8191       2674       5517

Add totals with the -t flag:

 free -t -m
             total       used       free     shared    buffers     cached
Mem:         16056       9029       7027          0        233       1093
-/+ buffers/cache:       7701       8354
Swap:         8191       2674       5517
Total:       24248      11703      12545

So in this case I am using 7701 MB of memory, while 8354 MB is free for use.

To get a quick glance, you can have a look at the file /proc/meminfo, grep for the highlights, like this:

 egrep  'Mem|Cache|Swap' /proc/meminfo
MemTotal:       16442312 kB
MemFree:         7255224 kB
Cached:          1120380 kB
SwapCached:        45632 kB
SwapTotal:       8388600 kB
SwapFree:        5650100 kB

A good option for finding out if a server is swapping, is by using vmstat:

oracle@myserver# vmstat -w 10 4
procs -----------------------memory---------------------- ---swap-- -----io---- -system-- --------cpu--------
 r  b         swpd         free         buff        cache   si   so    bi    bo   in   cs  us  sy  id  wa  st
 3  0      2772764       659396        20340     10764836    4    4    19     9    3    4  13   6  81   0   0
 6  0      2771740       735076        20364     10766444   82    0    82     7 68360 52089  57  30  13   0   0
10  0      2771484       767816        20376     10766628    8    0    12     4 67349 52155  55  31  15   0   0
 7  0      2771228       747480        22832     10768888   34    0   495    12 67799 52119  57  30  13   0   0

where * The flag -w indicates wide output * Sample every 10 second * 4 iterations Columns: * si: Amount of memory swapped in from disk (/s) * so: Amount of memory swapped to disk (/s) When a lot of negative swapping occurs the value of "so" (swap out) is increasing.

How to resolve PLS-00201: identifier 'DBMS_SYSTEM.SET_BOOL_PARAM_IN_SESSION'

During migration of an EBS (E-Business Suite) database, I was left with some packages in the APPS schema that couldn't be compiled.

SQL> alter package apps.ad_parallel_updates_pkg compile body;

Warning: Package Body altered with compilation errors.

SQL> show errors
Errors for PACKAGE BODY APPS.AD_PARALLEL_UPDATES_PKG:

LINE/COL ERROR
-------- -----------------------------------------------------------------
338/8    PL/SQL: Statement ignored
338/8    PLS-00201: identifier 'DBMS_SYSTEM.SET_BOOL_PARAM_IN_SESSION'
         must be declared

I first tried granting execute on dbms_system directly to the user app - no luck.

Then I found the following blog post

https://blogs.oracle.com/mandalika/entry/resolving_pls_00201_identifier_dbms

Which points to the following solution:

SQL> create public synonym dbms_system for dbms_system;

Synonym created.

SQL> grant execute on dbms_system to apps;

Grant succeeded.

SQL> alter package apps.ad_parallel_updates_pkg compile body;

Package body altered.

SQL>

Cardinality, Selectivity, Projection and Selection - definitions

From Oracle documentation:

Cardinality

The ratio of distinct values to the number of table rows. A column with only two distinct values in a million-row table would have low cardinality

Selectivity

In a query, the measure of how many rows from a row set pass a predicate test, for example, WHERE last_name = 'Smith'. A selectivity of 0.0 means no rows, whereas a value of 1.0 means all rows. A predicate becomes more selective as the value approaches 0.0 and less selective (or more unselective) as the value approaches 1.0.

Projection

The ability of a SELECT statement to choose a *subset* of the columns in a given table.
In other words, this corresponds to the column listing in the SELECT statement.

Selection

The ability of a SELECT statement to choose a subset of rows in a given table.
In other words, selection corresponds to the WHERE clause of the statement.

Preparations to make before running dbms_redefinition on a large table

To avoid ORA-01555 "snapshot too old", you should take the following precaution before starting an online redefinition of a large table:

1. If possible, create a new BIGFILE undo tablespace:

CREATE BIGFILE UNDO TABLESPACE UNDOTBS2 DATAFILE
  '/u02/oradata/proddb01/undotbs02_01.dbf' SIZE 128M AUTOEXTEND ON NEXT 32M MAXSIZE UNLIMITED
RETENTION NOGUARANTEE;

2. Make the new UNDO tablespace database default:

ALTER SYSTEM SET undo_tablespace='UNDOTBS2' SCOPE=BOTH;

3. Alter the retention of UNDO data to GUARANTEED retention:

ALTER TABLESPACE UNDOTBS2 RETENTION GUARANTEE;

4. If possible, create a new BIGFILE temporary tablespace:

CREATE BIGFILE TEMPORARY TABLESPACE TEMP2 TEMPFILE
'/u02/oradata/proddb01/temp2_01.dbf' SIZE 1G AUTOEXTEND ON NEXT 128M MAXSIZE UNLIMITED
EXTENT MANAGEMENT LOCAL UNIFORM SIZE 1M;

5. Make the new temporary tablespace the database default:

ALTER DATABASE DEFAULT TEMPORARY TABLESPACE "TEMP2";

6. Empty the recyclebin. As sysdba:

PURGE RECYCLEBIN;

7. Adjust the parameter undo_retention
Set the parameter high enough to sustain operation of the database for the amount of time you expect the redefintion to last.
For example, if you expect the redefinition to run for 48 hours, set the undo_retention to 172800 seconds:

alter system set undo_retention = 172800 scope=memory;

When the online redefinition has completed, return the UNDO tablespace to its normal retention:

ALTER TABLESPACE UNDOTBS2 RETENTION NOGUARANTEE;

About RETENTION GUARANTEED:

... specifies that Oracle Database should preserve unexpired undo data in all undo segments of tablespace even if doing so forces the failure of ongoing operations that need undo space in those segments. This setting is useful if you need to issue an Oracle Flashback Query or an Oracle Flashback Transaction Query to diagnose and correct a problem with the data.

About RETENTION NOGUARANTEE:

... returns the undo behavior to normal. Space occupied by unexpired undo data in undo segments can be consumed if necessary by ongoing transactions. This is the default

Source: Oracle Documentation

More about undo retention can be found here

Setting the minimum undo retention period

How to enable OLAP in an Oracle 11gR2 database

First, check that the prerequisites are fulfilled. The components below must be installed and valid before proceeding.

select comp_id,  comp_name, version,status from dba_registry where comp_id in ('XDB','XML','JAVAVM','EXF');

COMP_ID    COMP_NAME                      VERSION    STATUS
---------- ------------------------------ ---------- ----------
XDB        Oracle XML Database            11.2.0.4.0 VALID
EXF        Oracle Expression Filter       11.2.0.4.0 VALID
JAVAVM     JServer JAVA Virtual Machine   11.2.0.4.0 VALID
XML        Oracle XDK                     11.2.0.4.0 VALID

If java virtual machine is not installed:

sqlplus / as sysdba
set echo on
spool JServer.log
@?/javavm/install/initjvm.sql;
@?/xdk/admin/initxml.sql;
@?/xdk/admin/xmlja.sql;
@?/rdbms/admin/catjava.sql;
spool off

If XML DB is not yet install, you need to follow "Master Note for Oracle XML Database (XDB) Install / Deinstall (Doc ID 1292089.1)" from Oracle Support


If Oracle Expression Filter is not installed:

sqlplus / as sysdba
@?/rdbms/admin/catexf.sql

1. Start by shutting down the database:

sqlplus / as sysdba
shutdown immediate

2. Prepare your ORACLE_HOME by relinking the "oracle" executable.

For Oracle 11R2 and above, use the chopt utility. It was provided to help DBAs add new options and implicitly relink the binaries.

chopt enable olap

Writing to /u01/oracle/product/11204/install/enable_olap.log...
/usr/bin/make -f /u01/oracle/product/11204/rdbms/lib/ins_rdbms.mk olap_on ORACLE_HOME=/u01/oracle/product/11204
/usr/bin/make -f /u01/oracle/product/11204/rdbms/lib/ins_rdbms.mk ioracle ORACLE_HOME=/u01/oracle/product/11204

For versions prior to 11gR2:

cd $ORACLE_HOME/rdbms/lib
  make -f ins_rdbms.mk olap_on
  make -f ins_rdbms.mk ioracle

3. Open your database:

sqlplus / as sysdba
startup

4. Set up OLAP

cd $ORACLE_HOME/olap/admin
sqlplus / as sysdba
spool install_olap.log
@olap.sql SYSAUX TEMP

5. Verify that OLAP was installed:

select * from v$option where parameter='OLAP';

PARAMETER                      VALUE
------------------------------ ------------------------------
OLAP                           TRUE

How to check if the OLAP option is installed in the database

select comp_name, version, status from dba_registry  where comp_name like '%OLAP%' order by 1 DESC;

Typical output if OLAP is installed:

COMP_NAME	VERSION	STATUS
Oracle OLAP API	11.2.0.4.0	VALID
OLAP Catalog	11.2.0.4.0	VALID
OLAP Analytic Workspace	11.2.0.4.0	VALID

You can also use:

select * from v$option where parameter='OLAP';

PARAMETER	VALUE
OLAP	TRUE

How to manually register the database with the listener

Sometimes there may be a delay before pmon register itself with the listener.

lsnrctl status will show

The listener supports no services
The command completed successfully

To manually force pmon to register, execute

alter system register;