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28 Cards in this Set
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- 3rd side (hint)
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Complete this SQL statement so that you can view whether you have any contention on your rollback segments:
SQL> SELECT class, count 2 from "x" (enter x variable in answer) 3 WHERE class IN |
v$waitstat
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The advantage of small rollback segments is that they tend to remain what?
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cached
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For OLTP, try to create many small rollback segments of perhaps "x" size and with "y" # of extents. (optimally with a rollback segment available for each transaction).
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x=10kb-20kb size, y=2-4 extents
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The small size of the rollback segments provides for a better chance of being cached in the SGA. There is probably very little dynamic growth of the extents.
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For long queries, a good rule of thumb is to create rollback segments approximately x% the size of the largest table.
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10%
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(most SQL statements affect only about x% of the data in a table).
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It's is appropriate to create rollback segments approximately x% the size of the largest table.
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10%
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For transactions that update large amounts of data, you should also use a larger rollback segment.
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Which of the following is an advantage to using small
rollback segments? |
More likely to remain cached in the SGA
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In general, you can obtain the best performance of rollback I/O when there are approximately "x" # of extents of equal size per rollback segment.
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x=10 to 20
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As stated earlier, you want to avoid the dynamic space management that causes additional overhead and transactional delays. To determine whether rollback segments are a problem, look in this dynamic performance table?
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V$ROLLSTAT
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This type of extent is defined as extents with uncommitted transaction data.
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active
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The number of times the rollback segment decreased in size. Each decrease may be one or more extents at a time.
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shrinks
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using v$rollstat query output, if the average rollback extent size is close to the size set for "x", then "x" is set correctly. If either extends or shrinks is high, you must increase the value for "x".
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optimal
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In user accounts, "x" is used to assign privileges that allow the user to access different objects and operations, while "y" is used to control the amount of system resources that the user is allowed to consume.
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x=role, y=profile
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You can create user accounts using these 3 methods?
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Enterprise Manager, Security Manager, or the CREATE USER command
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You must have this system privilege to create a new user.
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create user
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There is little you can do with the CREATE USER command that you cannot do with the graphical tools except
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quota
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You must have the this system privilege to modify a user account.
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alter user
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Where privileges are given via the "x", limitations on the user are typically assigned via the "y".
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x=role, y=profile
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These are created as an easier way of setting limitations on users.
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profiles
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how many profiles can a user be assigned?
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1
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primary way of allocating system privileges to the user community
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roles
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Add Privileges to Roles is available by right-clicking on a role in which graphical utility?
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security manager
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Use this command to assign roles or system privileges to roles or users.
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grant
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This command is just the opposite of the GRANT command; it will take a role or system privilege away from a user or role.
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revoke
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use this command to completely take away a role from the system.
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drop
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works with the GRANT command to specify that the grantee has the right to pass this role or system privilege to any other user or role in the system.
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with admin option
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The Oracle sequence generator can generate sequential numbers of up to how many digits, without having to manually lock records
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38
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Sequences are incremented as they are accessed, independent of rollback or commit. If a transaction generates a sequence and then rolls back, the sequence is not replaced. This is referred to as?
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sequential value holes
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It can be efficient to use cached sequences to generate unique?
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primary key values
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