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Sybase DBA Interview Q - Download as PDF File .pdf), Text File .txt) or read online. Sybase DBA Interview Questions. locks etc) Answer 3 First I will look for . Sybase DBA Interview Questions- 2 -. Question 1. What is the purpose of sybsystemdb? Answer 1. Sybsytemdb is basically used for distributed transaction . Sybase Interview Questions and Answers. Are you a Database Administrator? Need to update DBA technical knowledge or need to prepare for a job interview?.
There are several ways to accomplish this. One way is to drop the clustered index and re-create it. Another way is to bcp out, truncate table deallocate extents and then bcp in the data allocating only enough extents to hold the data Explain what happens when clustered index is created? What happens when non-clustered index was created? A leaf level is created by copying the specified index columns. The leaf level is sorted and uses pointers to the associated data pages.
The Backup Server Why would we define a fill factor when creating an index? How do we increase the size of database? Alter database What utility does sybase use to import large volumes of data? BCP When fast bcp is used to load data, what effect does it have on the transaction log? When fast BCP is used syb does not log any transactions. What is stored in syslogs? Would frequent transaction log dumps be used for an application classified as decision support or on line transaction processing?
On line transaction processing What happens when we try to create unique index on a column that contains duplicate values? Does Syb allows null values in a column with unique index? We can complete update the process purpose. It updates the all transactions, page allocations. Describe some scenarios that would cause the transaction log to fill up. What are the DBCC commands? If the database corrupted, then we can repair through dbcc dbrepair.
If the transactions log is full. If an old transaction remains open and is causing the log to fill up, what should you do?
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How to change configure the values? If syslogs of a database was full what are the steps taken? The leaf level of the clustered index is the data.
What does update statement do? What are the constraints in sybase? What does dump database does and dump tran does?
Will a file containing rows that have negative values for column b be added during a bulk-copy? What command you use to change the default value in column b to 5?
How many pages are allocated when a table is created? What is difference between varchar and char? How many no of triggers can be created on a table?
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You usually wind up with more tables. You can have more clustered indexes you get only one per table so you get more flexibility in tuning queries. Index searching is often faster, since indexes tend to be narrower and shorter.
More tables allow better use of segments to control physical placement of data. You usually wind up with fewer indexes per table, so data modification commands are faster.
You wind up with fewer null values and less redundant data, making your database more compact. Triggers execute more quickly if you are not maintaining redundant data. Data modification anomalies are reduced. Normalization is conceptually cleaner and easier to maintain and change as you needs change.
While fully normalized databases require more joins, joins are generally very fast if indexes are available on the join columns.
The cost of finding rows already in the data cache is extremely low. Each database, including the system databases master, model, sybsystemprocs, and tempdb, has its own transaction log.
As modifications to a database are logged, the transaction log continues to grow until it is truncated, either by a dump transaction command or automatically if the trunc log on chkpt option is turned on as described below. This option is not recommended in most production environments where transaction logs are needed for media failure recovery, because it does not save the information contained in the log.
The transaction log on SQL Server is a write-ahead log.
After a transaction is committed, the log records for that transaction are guaranteed to have been written to disk. Changes to data pages may have been made in data cache but may not yet be reflected on disk. Transaction Logs and commit transaction When you issue a commit transaction, the transaction log pages are immediately written to disk to ensure recoverability of the transaction.
The modified data pages in cache might not be written to disk until a checkpoint is issued by a user or SQL Server or periodically as the data cache buffer is needed by other SQL Server users.
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Note that pages modified in data cache can be written to disk prior to the transaction committing, but not before the corresponding log records have been written to disk. This happens if buffers in data cache containing dirty pages are needed to load in a new page.
Transaction Logs and the checkpoint Process If the trunc log on chkpt option is set for a database, SQL Server truncates the transaction log for the database up to the page containing the oldest outstanding transaction when it issues a checkpoint in that database.
A transaction is considered outstanding if it has not yet been committed or rolled back. A checkpoint command issued by a user does not cause truncation of the transaction log, even when the trunc log on chkpt option is set.
Only implicit checkpoints performed automatically by SQL Server result in this truncation. These automatic checkpoints are performed using the internal SQL Server process called the checkpoint process.
The checkpoint process wakes up about every 60 seconds and cycles through every database to determine if it needs to perform a checkpoint. This determination is based on the recovery interval configuration parameter and the number of rows added to the log since the last checkpoint.
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Only those rows associated with committed transactions are considered in this calculation. If the trunc log on chkpt option is set, the checkpoint process attempts to truncate the log every sixty seconds, regardless of the recovery interval or the number of log records.
If nothing will be gained from this truncation, it is not done. Transaction Logs and the recovery interval The recovery interval is a configuration parameter that defines the amount of time for the recovery of a single database.
If the activity in the database is such that recovery would take longer than the recovery interval, the SQL Server checkpoint process issues a checkpoint. Because the checkpoint process only examines a particular database every 60 seconds, enough logged activity can occur during this interval that the actual recovery time required exceeds the time specified in the recovery interval parameter.
Note that the transaction log of the tempdb database is automatically truncated during every cycle of the checkpoint process, or about every 60 seconds. This occurs whether the trunc log on chkpt option is set on tempdb or not. Any SQL statement or set of statements that modifies data is a transaction and is logged.
These minimally logged operations cause the transaction log to get out of sync with the data in a database, which makes the transaction log useless for media recovery. Once a non-logged operation has been performed, the transaction log cannot be dumped to a device, but it can still be truncated. You must do a dump database to create a new point of synchronization between the database and the transaction log to allow the log to be dumped to device.
What Information Is Logged When a transaction is committed, SQL Server logs every piece of information relating to the transaction in the transaction log to ensure its recoverability.
The amount of data logged for a single transaction depends on the number of indexes affected, the amount of data changed, and the number of pages that must be allocated or deallocated. Certain other page management information may also be logged.Running the script populates table a and the transaction log at the same time, until tempdb is full.
What is the prerequisite for bcp? Why Do We Use Them?
Our Portals: Business Team AD is reporting the query slow performance, how will you investigate, pls consider all case. As you can see, this is a very straight-forward cursor procedure that loops through a table called CustomerTable and retrieves iRowId, vchCustomerNmbr and vchCustomerName for every row.