tt.execute(new TransactionCallbackWithoutResult() {
@Override
protected void doInTransactionWithoutResult(TransactionStatus arg0) {
// update the global quota
Quota quota = getUsedQuotaByLayerName(layerName);
quota.setBytes(quota.getBytes().negate());
String updateQuota = dialect.getUpdateQuotaStatement(schema, "tileSetId", "bytes");
Map<String, Object> params = new HashMap<String, Object>();
params.put("tileSetId", GLOBAL_QUOTA_NAME);
params.put("bytes", new BigDecimal(quota.getBytes()));
jt.update(updateQuota, params);
// delete the layer
log.info("Deleting disk quota information for layer '" + layerName + "'");
String statement = dialect.getLayerDeletionStatement(schema, "layerName");