---
title:  Using Indexes with Overflow Regions
---

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You can use indexes when querying on overflow regions; however, there are caveats.

The following are caveats for querying overflow regions:

-   You must use synchronous index maintenance for the region. This is the default maintenance setting.
-   The index FROM clause must specify only one iterator, and it must refer to the keys or entry values. The index cannot refer to the region’s entrySet.
-   The index data itself is not stored on (overflowed to) disk .

**Examples:**

The following example index creation calls DO NOT work for overflow regions.

``` pre
// This index will not work on an overflow region because there are two iterators in the FROM clause.
createIndex("secIdIndex", "b.secId","/portfolios pf, pf.positions.values b");

// This index will not work on an overflow region because the FROM clause specifies the entrySet
createIndex("indx1", "entries.value.getID", "/exampleRegion.entrySet() entries");
```

The following example indexes will work for overflow regions.

``` pre
createIndex("pkidIndex", "p.pkid", "/Portfolios p");

createIndex("indx1", "ks.toString", "/portfolio.keySet() ks");
```

The same working examples in gfsh:

``` pre
gfsh> create index -name="pkidIndex" --expression="p.pkid" --region="/Portfolios p"

gfsh> create index -name="indx1" --expression="ks.toString" --region="/portfolio.keySet() ks"
```