What is index block split?

Indexes are made up of a root block, branch blocks, and leaf blocks. 50/50 block split, where a new block is created and half the entries are contained in each of the blocks after the split. 99/1 block split, accommodating indexes where there are ever-increasing values and the new key value is the highest key.

What is index block?

An index block is a special type of block that returns a listing of assets from the CMS directory structure in the form of XML data. Assets like pages, files, folders, external links, and even other blocks can be returned as XML content.

What is leaf blocks in Oracle indexes?

Leaf blocks contain the indexed column value and ROWID of the table rows that they address.

What is reverse key index in Oracle?

Reverse key indexes literally reverse the bytes of the key value in the index to reduce block contention on sequence generated primary keys. Scalable Sequences were introduced in Oracle 18c as an alternative to using reverse key indexes.

How does a smaller blocksize reduce index leaf contention?

For indexes, a smaller blocksize means that there will be fewer keys per block, and fewer keys per block can reduce index leaf block contention by reducing the likelihood that any two tasks will be waiting for the same block.

What happens in a 90 / 10 index block split?

In a 90/10 index block split, we usually see that the data is being loaded in the same order as the index key.

Is there a way to remove emply index splits?

Instead, Oracle will mark the empty data block as a ‘deleted leaf node” The only way to remove emply index splits is to rebuild or claresce the index. Index splitting can cause contention: If another session is doing DML data while another task is attempting an index access, the task must wait on that index block split until it has finished.

When do you split an index block in Oracle?

When an index leaf block is full and a new row has to be inserted in the block Oracle will usually allocate a new leaf block, split the contents of the full block fairly evenly between two leaf blocks, then update various pointers to bring the index structure up to date.