Sql server difference faqs- 7

1.Difference between Checkpoint and Lazy Writer

S.No CheckPoint Lazy Writer

1 Flush dirty pages to Disk Flush dirty pages to disk

2 Flush only Data pages to disk Check for available memory and
removed Buffer pool (execution
plan/compile plan/ Data pages
/Memory objects)

3 Default, Occurs approximately Occurs depending upon memory
every 1 minute pressure and resource availability

4 Can be managed with sp_confige It is lazy, Sql server manages by its
-recovery interval option own.

5 Does not check the memory Monitor the memory pressure and try
pressure maintain the available free memory.

6 Crash recovery process will be No role in recovery
fast to read log as data file is
updated.

7 Occurs for any DDL statement Occurs per requirement

8 Occurs before Backup/Detach Occurs per requirement
command

9 Depends upon the configuration Works on Least recent used pages and
setting, we can control. removed unused plans first, no user
control.

10 For simple recovery it flush the No effect on recovery model.
tlog file after 70% full.

11 Can manually /Forcefully run No command for Lazy Writer
command “Checkpoint”

12 Very Less performance impact No performance impact

2.Difference between Mirroring and Log Shipping

S.No Mirroring Log Shipping

1 Principle can have single mirror Multiple stand by servers can be
possible.

2 Generally good to have 10 DB’s No limit
for one server

3 No data loss and can be used as May be some data loss as per schedule.

high availability like Clustering And secondary server takes some
manual work and time to be primary

4 Read log read and transfer the Transfer the log back up and restored
committed transaction through at standby server.
endpoints.

5 Only committed transaction Committed as well as uncommitted
and whole log backup restores.

6 PAGE repair is possible if N/A
principle database page gets
corrupt

7 Mirrored DB can only be accessed Secondary server can be reporting
using snapshot DB server (read-only)

8 Principle and Mirror server should Primary and secondary server should
have same edition be compatible server for restore.

9 Require FULL recovery model Require FULL or Bulk-Logged
recovery model

10 Requires Sql Server 2005 SP1 or Enterprise edition for Sql Server 2000
higher – Enterprise or Developer and even Standard edition for 2005 can
Editions works

11 Immediate data moved depending Can control the flow of data by
on SEND and WAIT queue scheduling jobs

12 As Immediate data moves, user As delay in data transfer can avoided
error reflects at mirrored DB user error.

3.Difference between Change Track and Change Data Capture – CDC in SQL Server 2008

S.No Change Track Change Data Capture

1 It is about fact: It is about the Data:
It captures only the fact as the Change data capture provides
tracking table has changed. It does historical change information for a
NOT capture the data. user table by capturing both the fact
Therefore, change tracking is that DML changes were made and the
more limited in the historical actual data that was changed.
questions it can answer compared
to change data capture. However,
for those applications that do not
require the historical information,
there is far less storage overhead
because of the changed data not
being captured

2 Storage: Storage:
Internal tables are placed on the When change data capture is enabled
same filegroup as the parent for a database, a few things are added
entity. You could use the to the database, including a new
sys.internal_tables catalog view schema (called cdc), some metadata
to show all the internal tables and tables, and a trigger to capture Data
parent entities. For example: Definition Language (DDL) events.
select name,
object_name(parent_id) as The two function names are,
parent_object from respectively,
sys.internal_tables fn_cdc_get_all_changes_ and
fn_cdc_get_net_changes_, with the
capture instance name appended. Note
that (like the change tracking feature)
this functionality requires the table to
have a primary key or other unique
index.

3 Supported on “Simple” recovery Prevents Log truncation.
model also. Forces full logging of some bulk
It is recommended that you use operations.
snapshot isolation when change
tracking is enabled. Snapshot One major point to note here is that
isolation itself can add significant once change data capture is enabled,
workload overhead and requires the transaction log behaves just as it
much more careful management does with transactional replication—
of tempdb. the log cannot be truncated until the
log reader has processed it. This means
a checkpoint operation, even in
SIMPLE recovery mode, will not
truncate the log unless it has already
been processed by the log reader.

4 It uses synchronous tracking Change Data Capture (CDC) uses the
mechanism. asynchronous process that reads the
once a database is enabled for transaction log.
change tracking, a version
number is instituted, which
allows ordering of operations

5 Change Tracking has minimal It has almost nil impact as it
impact on the system. asynchronous mechanism reads from
the transaction log.

6 It uses TempDB heavily It uses transaction log.

7 DDL Restriction: No such DDL restriction
There are restrictions on the DDL
that can be performed on a table
being tracked. The most notable
restriction is that the primary key
cannot be altered in any way. The

other restriction worth calling out
here is that an ALTER TABLE
SWITCH will fail if either table
involved has change tracking
enabled.

8 SQL Agent not needed t requires SQL Agent to be running.
SQL Agent Job & Transaction
Replication:
Two SQL Agent jobs may be created:
the capture job and the cleanup job. I
say "may be created" because the
capture job is the same as the one used
for harvesting transactions in
transactional replication.
If transactional replication is already
configured, then only the cleanup job
will be created and the existing log
reader job will also be used as the
capture job

9 Permission required to enable: Permission required to enable:
SYSADMIN DBOwner

4.Difference between Index Rebuild and Index Reorganize in SQL Server 2005

S.No Index Rebuild Index Reorganize

1 Index Rebuild drops the existing Index Reorganize physically
Index and Recreates the index reorganizes the leaf nodes of the index.
from scratch.

2 Rebuild the Index when an index Reorganize the Index when an index is
is over 30% fragmented. between 10% and 30% fragmented.

3 Rebuilding takes more server Always prefer to do Reorganize the
resources and uses locks unless Index.
you use the ONLINE option
available in 2005 Enterprise and
Development editions.

4 T-SQL for Rebuilding all T-SQL for Reorganize all Indexes of
Indexes of a particular table. a particular table.

USE AdventureWorks; USE AdventureWorks;
GO GO
ALTER INDEX ALL ON ALTER INDEX ALL ON
HumanResources.Employee HumanResources.Employee
REBUILD REORGANIZE
GO GO

Note: If fragmentation is below 10%, no action required.

5.Difference between User -defined SP and System-defined SP

S.No User-defined SP System-defined SP

1 Once we create User defined SP System defined sp are available in
in one database i.e available to master DB.These sp’s can be directly
only that database directly.i.e called from any DB
we cannot call it from some other
DB’s directly

2 UDSP will be used to fulfill the SDSP will be used for managing sql
user requirements server

Please visit my blog @ http://onlydifferencefaqs.blogspot.in/

Sql server difference faqs- 7

Recommended

More Related Content

What's hot (9)

Viewers also liked (18)

Similar to Sql server difference faqs- 7 (20)

More from Umar Ali (20)

Recently uploaded (20)

Sql server difference faqs- 7